Exploding Galaxies and other Catastrophysics

JWST cancellation by House of Representatives

2011-07-07T07:51:00.001-04:00

Neither unexpected, undeserved, disasterous or likely final.

Changed Targets of Interest

2011-04-29T19:23:00.002-04:00

I finally got around to making some long-needed changes to the links visible on the right hand side of this blog.

Laelaps, Not Exactly Rocket Science, Gene Expression, and the Primate Diaries "in Exile" are back in and/or are now working, finally catching up with all the moves associated with the great scienceblogs Pepsi kerfuffle about a year ago...
Deltoid, Sandwalk, john hawk's weblog, Bartholomew's notes, Crooked Timber and so finally got added as I read them often enough to make a direct link worthwhile.
My old non-astro blog got removed as I never update it any more.
Parasite of the Day, Molecule of the Day, Denialism Blog got removed as they're updated too infrequently. Sad, as they were great.
Uncertain Principles gets deleted because there isn't enough interesting science to offset his knee-jerk atheist-bashing.

IXO is dead, long live ATHENA

2011-04-16T11:58:00.002-04:00

IXO and LISA are dead as joint NASA/ESA missions, thanks to NASA funding woes and JWST's grotesque cost and time overruns. Nevertheless, ESA will go ahead with a smaller (800 million Euro) X-ray Observatory concept with limited NASA participation (the microcalorimeter, I hope?) called ATHENA... a nice naming joke I didn't get at first. A few years ago ESA's XEUS mission concept and NASA's Constellation-X mission concept merged to form the International X-ray Observatory (IXO). Now the Europeans are back alone ATHENA springs forth, as in Greek myth where Athena emerged from Zeus's forehead.

News from the IXO website.

An update on IXO from Nick White and Jay Bookbinder

US IXO Team,

This is an update on the discussions with the European Space Agency (ESA) at the recent ESA-NASA bilateral meeting. This was reported by Jon Morse (HQ Astrophysics Division Director), first, to the IXO and LISA teams on Tuesday, and then, at the Astrophysics NASA Advisory Committee (NAC) sub-committee meeting on Thursday afternoon.

IXO was one of three candidates competing for the L1 opportunity in ESA´s Cosmic Vision Program (2015-2025). The Astrophysics and Planetary decadal rankings and NASA´s constrained out-year resources projected in the President's FY12 budget request led ESA to conclude that none of the three mission concepts were feasible within the Cosmic Vision L1 schedule. Consequently, ESA has ended consideration of IXO and the other concepts as partnerships at the scale proposed in the New Worlds New Horizons decadal survey (NWNH) and EJSM/Laplace in Visions and Voyages for Planetary Science. Instead, ESA has begun a rapid definition effort that includes the formation of a new science team (to be announced shortly). That effort will identify science goals and a mission concept that can be implemented as part of an ESA-led mission launching in the early 2020´s for a cost to ESA of about 800M Euro. Revised mission concepts from the three science areas will be considered in a selection process tentatively foreseen in February 2012.

A future minor role for NASA in the new ESA-led X-ray mission, in particular contributions at the instrument level, has not been ruled out. NASA will participate in the new ESA science team through a "NASA HQ-empowered scientist." This will be a NASA civil servant scientist who will be the conduit for any engagement with the new ESA team.

Currently the decadal survey recommendations are centered on the IXO (and LISA) concept and partnerships. NASA HQ will NOT disband the current NASA IXO (and LISA) teams immediately, but will follow a deliberate path towards redirecting the NASA efforts in the context of the decadal survey recommendations. NASA's Astrophysics Division plans to continue base funding (assuming not-larger-than-anticipated cuts from Congress) for the IXO (and LISA) study team(s) through FY11 to continue the technology development and so that NASA can support any effort requested by ESA through the NASA representative. The HQ Astrophysics Division may at some point in the future engage the community about strategic investments in X-ray astrophysics and possible solicitations for new concept studies in the context of the NWNH priorities.

It is expected that in about one year´s time NASA will ask the NRC to prioritize possible NWNH investments for the rest of the decade, including funding possible NASA participation in an ESA L1 mission – which we hope will be the X-ray mission. This would be in the context of not only the ESA L1 mission selection, but also the M1 and M2 mission selections, and the JWST re-plan.

We plan to keep in communication with the US IXO team as this unfolds. And seek input from the community at the appropriate times.

Feel free to forward this note to all interested parties.

Please let us know if you have any questions.

Nick White,

Jay Bookbinder

SDO images of the February 15th X2 Solar Flare

2011-02-26T11:30:00.005-05:00

It has been a while since I've had any time to even think about astronomy, but today I've got to do some work on a final grant report and while waiting for some software I need to download I thought I'd make some false color images of before and after last week's X2 class solar flare (Feb 15, 2011, 0152 UTC). This is the first X-class flare of the new solar cycle.

The left hand side shows 4500 Angstrom (in red), 1600 Angstrom (in green) and 94 Angstrom (in blue) images taken with the Solar Dynamics Observatory's AIA instrument superimposed on one another. The right hand panels are 304 Angstrom (red), 193 Angstrom (green) and 94 Angstrom (blue).

Something I mean to do is to find out by how much the Sun's EUV/X-ray luminosity increases during flaring, and what contribution to the total solar bolometric luminosity the normal and active corona provide.

Image were obtained in FITS format from the Virtual Solar Observatory, and superimposed using ds9.

2010-10-09T15:11:00.003-04:00

A few years ago I blogged a little bit about (Sir) Fred Hoyle and the tendency of some scientists to turn into cranks in the later life ("Fred Hoyle and the Venusian Pox").

Via John Hawks Weblog I came across an interesting article by Robin McKee on whether Hoyle's prickly nature or later lunacy (astronomy joke, sorry, I couldn't resist) cost him the Nobel Prize (his long time collabor Willy Fowler got the Nobel for work that Hoyle and he had done). It is worth reading if you find Hoyle interesting.

Seen from this perspective, Hoyle was the victim of his own intemperate nature, while the Nobel prize committee was guilty of a petty lack of objectivity. But there are other ways of looking at the issue, says British scientist Sir Harry Kroto, winner of the 1996 Nobel prize for chemistry. A Nobel is not just an award for a piece of work but is a recognition of a scientist's overall reputation, he believes . And by that definition, Hoyle – who died in 2001, never having recanted his belief in the steady state theory even when it was clearly demonstrated to be wrong – was unworthy of a prize [emphasis mine].

Rendering equations on the web: MathJax

2010-10-09T11:26:00.004-04:00

Previously I've mentioned codecog's online equation editor, which is pretty useful for generating images of LaTeX-rendered equations for use in web pages and powerpoint presentations.

Thanks to the latest version of doxygen, I've just discovered something even more useful: MathJax. It is an open source javascript display engine for math than works in all modern browsers, supports LaTeX and MathML, and allows copy and paste into LaTeX, Word, Mathematic. Wikipedia etc. Pretty amazing.

NAS's Astro2010 Decacal Survey recommendations

2010-08-16T18:03:00.000-04:00

The National Academies of Sciences has released its Astro2010 decadal survey report and recommendations. A PDF of the release presentation is also available on that site. The panel's recommendations influence what programs NASA, NSF and DOE pursue and fund in astronomy and astrophysics for the next decade, so this is a big deal.

So far I've only read the presentation, and looked at Steinn Sigurdsson's comments on his blog [1, 2], so what follows is by no means a complete and final assessment.

My personal take is that its a mix of the good and the bad.

Whats good (from my perspective at least):

A strong endorsement and emphasis on revitalizing the Explorer class mission program. This had suffered badly under O'Keefe and Griffin.
A strong recognition of the importance of feedback, and flows of matter and energy into and out of galaxies (the 8th, 9th, and 10th points on slide 9 of the PDF copy of presensation).

Whats bad:

IXO ranks 4th, behind some wide field IR telescope focussed on Dark Energy (yawn, a couple of billion bucks to get one not-very-interesting number) and LISA. IXO will only get $180m in the next decade, so basically that pushes it back to ~2030? And probably kills its chances in the ESA mission rankings too. Given that Constellation-X (IXO's forerunner prior to the merger with ESA) came 2nd (after JWST) in the previous decadal and IXO thought it had a good chance of coming 1st this time the current ranking is a real blow.
LISA is somehow ranked as lower risk (and cheaper) than IXO! Seriously?
Funding for astrophysics doesn't look like it going to get better.
Unless you're an optical/IR astronomer, or the three gravitational wave astronomers, you're in for a bad decade and a half. X-ray astronomy, UV astronomy, and radio seem to be in trouble.
From my perspective there is a disconnect between the science priorities for the next decade and the missions endorsed. Feedback and the galaxy/IGM interconnection isn't going to be answered by JWST, WFIRST, LISA or any Explorer mission

Still alive

2010-06-26T11:01:00.004-04:00

I'm still alive, just rather busy settling into the new job and the added commuting. When I have time I'll get back to posting. In the mean time:

Space.com has a short article with more images of IKAROS's solar sail (mentioned previously here).
NASA and NOAA engineers have got GOES-P's Solar X-ray Imager working again (see also a Space.com article). Hooray X-rays!

Japanese satellite succesfully deploys solar sail

2010-06-11T15:50:00.002-04:00

JAXA's IKAROS satellite has successfully deployed it solar sail and is getting power from the thin film solar panels. It'll be another six month's before we'll know whether the next part of the mission, actually being propelled by radiation pressure on the sail, is successful.

The JAXA press release has a really nice graphic explaining how the sail was unfurled.

For more on solar sails, see the SolarSailWiki.

Interesting Astrophysics: June 01 to June 11

2010-06-11T09:37:00.002-04:00

This is the final edition of Interesting Astrophysics with me working as a professional astrophysicist, as I start a new job outside astronomy next week. If I have the spare time at home I may try to continue this series, but perhaps at a reduced rate.

Nevertheless, there is some interesting stuff to look at. Molecular gas in starbursts is the subject of the Bothwell et al, Naylor et al, and Feruglio et al papers. In terms of winds, Muzic et al discuss possible/futher evidence of a wind within the central regions of our own galaxy (I still remain somewhat sceptical that the Milky Way hosts a true galactic wind), Kobulnicky & Martin present X-ray observations of the dwarf starburst Henize 2-10, Feruglio et al claim there is a hugely energetic molecular outflow in Markarian 231 that can only be power by an AGN, and Fischer discuss the geometry of the outflow in the central kiloparsec of the Seyfert 2 galaxy Mrk 573. Randall Smith and collaborators have posted two interesting X-ray line diagnostics papers, for all your X-ray spectroscopists out there.

Galaxies and Starbursts

AKARI infrared observations of edge-on spiral galaxy NGC 3079
Mitsuyoshi Yamagishi, Hidehiro Kaneda, Daisuke Ishihara, Shinya Komugi, Takashi Onaka, Toyoaki Suzuki, arXiv:1005.5251 [pdf, ps, other]
Comments: 15 pages, 7 figures, accepted for publication in PASJ

High-resolution CO and radio imaging of ULIRGs: extended CO structures and implications for the universal star formation law
M. S. Bothwell, S. C. Chapman, L. Tacconi, Ian Smail, R. J. Ivison, C. M. Casey, F. Bertoldi, R. Beswick, A. Biggs, A. W. Blain, P. Cox, R. Genzel, T. R. Greve, R. Kennicutt, T. Muxlow, R. Neri, A. Omont, 2010, MNRAS, 405, 219
Full Text: HTML, PDF (Size: 1391K)

From their abstract: "We find a difference in size between the CO and radio emission regions, and as such we suggest that using the spatial extent of the CO emission region to estimate the surface density of star formation may lead to error. This size difference also causes the star formation efficiencies within systems to vary by up to a factor of 5. We also find, with our new accurate sizes, that SMGs lie significantly above the KS relation, indicating that stars are formed more efficiently in these extreme systems than in other high- z star-forming galaxies."

A Census of the High-Density Molecular Gas in M82
B. J. Naylor, C. M. Bradford, J. E. Aguirre, J. J. Bock, L. Earle, J. Glenn, H. Inami, J. Kamenetzky, P. R. Maloney, H. Matsuhara, H. T. Nguyen, J. Zmuidzinas, arXiv:1006.1964 [pdf, ps, other]
Comments: 15 pages (using emulateapj.cls), 6 figures, submitted to the Astrophysical Journal

From their abstract: "We present a three-pointing study of the molecular gas in the starburst nucleus of M82 based on 190 - 307 GHz spectra obtained with Z-Spec at the Caltech Submillimeter Observatory. We measure intensities or upper-limits for 20 transitions, including several new detections of CS, HNC, C2H, H2CO and CH3CCH lines. We combine our measurements with previously-published measurements at other frequencies for HCN, HNC, CS, C34S, and HCO+ in a multi-species likelihood analysis constraining gas mass, density and temperature, and the species' relative abundances. We find some 1.7 - 2.7 x 10^8 M_sun of gas with n_H2 between 1 - 6 x 10^4 cm^-3 and T > 50 K. While the mass and temperature are comparable to values inferred from mid-J CO transitions, the thermal pressure is a factor of 10 - 20 greater."

Their median thermal pressure estimate P/k ~ 10^6.4 K cm^-3 for the molecular gas, is a little lower than our (Strickland & Heckman 2009) estimates for the very hot gas in the starburst (P/k ~10⁷), but for astrophysical work that's actually pretty close - its certainly closer than some other estimates in the literature. Nor would I expect the molecular gas to be in exact thermal pressure equilibrium with the hot gas.

Cometary shaped sources at the Galactic Center - Evidence for a wind from the central 0.2 pc
K. Muzic, A. Eckart, R. Schoedel, R. Buchholz, M. Zamaninasab, arXiv:1006.0909 [pdf, other]
Comments: to appear in A&A

Abstract in full: "In 2007 we reported two cometary shaped sources in the vicinity of Sgr A* (0.8" and 3.4" projected distance), named X7 and X3. The symmetry axes of the two sources are aligned to within 5 degrees in the plane of the sky and the tips of their bow-shocks point towards Sgr A*. Our measurements show that the proper motion vectors of both features are pointing in directions more than 45 deg away from the line that connects them with Sgr A*. This misalignment of the bow-shock symmetry axes and their proper motion vectors, combined with the high proper motion velocities of several 100 km/s, suggest that the bow-shocks must be produced by an interaction with some external fast wind, possibly coming from Sgr A*, or stars in its vicinity. We have developed a bow-shock model to fit the observed morphology and constrain the source of the external wind. The result of our modeling allows us to estimate the velocity of the external wind, making sure that all likely stellar types of the bow-shock stars are considered. We show that neither of the two bow-shocks (one of which is clearly associated with a stellar source) can be produced by influence of a stellar wind of a single mass-losing star in the central parsec. Instead, an outflow carrying a momentum comparable to the one contributed by the ensemble of the massive young stars, can drive shock velocities capable of producing the observed cometary features. We argue that a collimated outflow arising perpendicular to the plane of the clockwise rotating stars (CWS), can easily account for the two features and the mini-cavity. However, the collective wind from the CWS has a scale of >10''. The presence of a strong, mass-loaded outbound wind at projected distances from Sgr A* of <1'' is in fact in agreement with models that predict a highly inefficient accretion onto the central black hole due to a strongly radius dependent accretion flow."

Exploring the Origin and Fate of the Magellanic Stream with Ultraviolet and Optical Absorption
Andrew J. Fox, Bart P. Wakker, Jonathan V. Smoker, Philipp Richter, Blair D. Savage, Kenneth R. Sembach, arXiv:1006.0974 [pdf, ps, other]
Comments: Accepted for publication in ApJ. 18 pages, 7 figures, all in color

From their abstract: "Summing over the low-ion and high-ion phases, we derive conservative lower limits on the ratio N(total H II)/N(H I) of >19 toward NGC 7469 and >330 toward Mrk 335, showing that along these two directions the vast majority of the Stream has been ionized. The presence of warm-hot plasma together with the small-scale structure observed at 21 cm provides evidence for an evaporative interaction with the hot Galactic corona. This scenario, predicted by hydrodynamical simulations, suggests that the fate of the MS will be to replenish the Galactic corona with new plasma, rather than to bring neutral fuel to the disk."

The Diffuse and Compact X-ray Components of the Starburst Galaxy Henize~2-10
Henry A. Kobulnicky, Crystal L. Martin, arXiv:1006.1189 [pdf, ps, other]
Comments: Accepted for publication in The Astrophysical Journal; a version with high-resolution figures can be found at this http URL

From their abstract: "Chandra X-ray imaging spectroscopy of the starburst galaxy Henize 2-10 reveals a strong nuclear point source and at least two fainter compact sources embedded within a more luminous diffuse thermal component. ...Two-temperature solar-composition plasmas (kT~0.2 keV and kT~0.7 keV) fit the diffuse X-ray component as well as single-temperature plasmas with enhanced alpha/Fe ratios. Since the observed radial gradient of the X-ray surface brightness closely follows that of the Halpha emission, the composition of the X-ray plasma likely reflects mixing of the ambient cool/warm ISM with an even hotter, low emission measure plasma, thereby explaining the ~solar ISM composition. Aperture synthesis 21-cm maps show an extended neutral medium to radii of 60" so that the warm and hot phases of the ISM, which extend to ~30", are enveloped within the 8x10^20 /cm^2 contour of the cool neutral medium. This extended neutral halo may serve to inhibit a starburst-driven outflow unless it is predominantly along the line of sight. The high areal density of star formation can also be reconciled with the lack of prominent outflow signatures if Henize 2-10 is in the very early stages of developing a galactic wind."

Black Holes and AGN

Quasar feedback revealed by giant molecular outflows
Chiara Feruglio, Roberto Maiolino, Enrico Piconcelli, Nicola Menci, Herve' Aussel, Alessandra Lamastra, Fabrizio Fiore, arXiv:1006.1655 [pdf, ps, other]
Comments: Submitted for publication in A&A Letters. 4 pages, 3 figures

From their abstract: "We used the IRAM PdBI to observe the CO(1-0) transition in Mrk 231, the closest quasar known. We detect broad wings of the CO line, with velocities up to 750 km/s and spatially resolved on the kpc scale. Such broad CO wings trace a giant molecular outflow of about 2000 MSun/year, far larger than the ongoing star-formation rate (~200 MSun/year) observed in the host galaxy. This wind will totally expel the cold gas reservoir in Markarian 231 in less than 1e7 yrs, therefore halting the star-formation activity on the same timescale. The inferred kinetic energy in the molecular outflow is ~4e44 erg/s, corresponding to 7% of the AGN bolometric luminosity, which is very close to the fraction expected by models ascribing quasar feedback to highly supersonic shocks generated by radiatively accelerated nuclear winds. Instead, the contribution by the SNe fall short by orders of magnitude to account for the outflow kinetic energy."

There is going to be some skepticism about this paper in the superwind community, given the uncertainties in CO to hydrogen conversion factors. In terms of the larger scale (10+ kpc) superwind Mrk 231 is not that different from other ULIRGs with winds.

Modeling the Outflow in the Narrow-Line Region of Markarian 573: Biconical Illumination of a Gaseous Disk
T. C. Fischer, D. M. Crenshaw, S. B. Kraemer, H. R. Schmitt, M. L. Trippe, arXiv:1006.1875 [pdf]
Comments: 20 pages, 5 figures (1 color), to be published in The Astronomical Journal
Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

Abstract in full: "We present a study of the outflowing ionized gas in the resolved narrow-line region (NLR) of the Seyfert 2 galaxy Mrk 573, and its interaction with an in- ner dust/gas disk, based on Hubble Space Telescope (HST) WFPC2 and STIS observations. From the spectroscopic and imaging information, we determined the fundamental geometry of the outflow and inner disk, via two modeling pro- grams used to recreate the morphology of these regions imaged with HST. We also determined that the bicone of ionizing radiation from the Active Galactic Nucleus (AGN) intersects with the inner disk, illuminating a section of the disk including inner segments of spiral arms, fully seen through structure mapping, which appear to be outflowing and expanding. In addition, we see high velocities at projected distances of \geq 2'' (- 700 pc) from the nucleus, which could be due to rotation or to in situ acceleration of gas off the spiral arms. We find that the true half opening angle of the ionizing bicone (53 degrees) is much larger than the apparent half-opening angle (34 degrees) due to the above geometry, which may apply to a number of other Seyferts as well."

X-ray Astronomy

Ionization Equilibrium Timescales in Collisional Plasmas
Randall K. Smith, John P. Hughes, arXiv:1006.0254 [pdf, ps, other]
Comments: 4 pages, 2 figures. Accepted for publication by the Astrophysical Journal

Full abstract: "Astrophysical shocks or bursts from a photoionizing source can disturb the typical collisional plasma found in galactic interstellar media or the intergalactic medium. The spectrum emitted by this plasma contains diagnostics that have been used to determine the time since the disturbing event, although this determination becomes uncertain as the elements in the plasma return to ionization equilibrium. A general solution for the equilibrium timescale for each element arises from the elegant eigenvector method of solution to the problem of a non-equilibrium plasma described by Masai (1984) and Hughes & Helfand (1985). In general the ionization evolution of an element Z in a constant electron temperature plasma is given by a coupled set of Z+1 first order differential equations. However, they can be recast as Z uncoupled first order differential equations using an eigenvector basis for the system. The solution is then Z separate exponential functions, with the time constants given by the eigenvalues of the rate matrix. The smallest of these eigenvalues gives the scale of slowest return to equilibrium independent of the initial conditions, while conversely the largest eigenvalue is the scale of the fastest change in the ion population. These results hold for an ionizing plasma, a recombining plasma, or even a plasma with random initial conditions, and will allow users of these diagnostics to determine directly if their best-fit result significantly limits the timescale since a disturbance or is so close to equilibrium as to include an arbitrarily-long time"

Hooray, it has finally appeared!

A New Calculation of Ne IX Line Diagnostics
Randall K. Smith, Guo-Xin Chen, Kate Kirby, Nancy S. Brickhouse, arXiv:1006.0667 [pdf, ps, other]
Journal-ref: 2009, ApJ, 700, 679

Their abstract: "We describe the effect that new atomic calculations, including fully-relativistic R-matrix calculations of collisional excitation rates and level-specific dielectronic and radiative recombination rates, have on line ratios from the astrophysically significant ion Ne IX. The new excitation rates systematically change some predicted Ne IX line ratios by 25% at temperatures at or below the temperature of maximum emissivity (4x10^6 K), while the new recombination rates lead to systematic changes at higher temperatures. The new line ratios are shown to agree with observations of Capella and sigma^2 CrB significantly better than older line ratios, showing that 25-30% accuracy in atomic rates is inadequate for high-resolution X-ray observations from existing spectrometers."

This paper is from last year, but worth keeping in mind.

Numerical Astrophysics and Hydrodynamics

Inviscid SPH
Lee Cullen, Walter Dehnen, arXiv:1006.1524 [pdf, ps, other]
Comments: 14 pages (15 in arXiv), 15 figures, accepted for publication in MNRAS

Abstract in full: "In smooth-particle hydrodynamics (SPH), artificial viscosity is necessary for the correct treatment of shocks, but often generates unwanted dissipation away from shocks. We present a novel method of controlling the amount of artificial viscosity, which uses the total time derivative of the velocity divergence as shock indicator and aims at completely eliminating viscosity away from shocks. We subject the new scheme to numerous tests and find that the method works at least as well as any previous technique in the strong-shock regime, but becomes virtually inviscid away from shocks, while still maintaining particle order. In particular sound waves or oscillations of gas spheres are hardly damped over many periods."

Stars, Supernovae and Planets

Atmospheric mass loss by stellar wind from planets around main sequence M stars
Jesus Zendejas, Antigona Segura, Alejandro Raga, arXiv:1006.0021 [pdf, ps, other]
Comments: Icarus, submitted. 18 pages, 6 figures

They conclude that for late type M dwarfs (later than M5),most planets within the habitable zone may have lost their atmospheres in 1 Gyr or less.

The Evolution of Cloud Cores and the Formation of Stars
Avery E. Broderick, Eric Keto, arXiv:1006.0733 [pdf, ps, other]
Comments: 12 pages, 7 figures, submitted to ApJ

Jupiter gets hit again!

2010-06-04T08:41:00.003-04:00

Just last year an asteroid hit Jupiter. At that time no one saw the impact directly, but the aftermath was spotted by amateur astronomers.

Now Jupiter has been hit again, and some amateurs astronomers were lucky enough to capture the impact directly. Amazingly awesome.

For more info see this Bad Astronomy post.

What I want for my birthday: a table-top X-ray laser

2010-06-02T16:02:00.003-04:00

Chad Orzel has a nice post at Uncertain Principles about work at JILA on creating table-top devices that can produce pulses of coherent X-ray emission, i.e. X-ray lasers, with energies of of several hundred eV to ~1 keV.

Given the current difficulties in producing effectively parallel beams of X-ray for use in calibrating X-ray mirrors and detectors this new technology may be very useful.

Interesting Astrophysics: 17 May to 28 May

2010-05-28T09:24:00.002-04:00

The final batch of interesting preprints (and a few accepted papers) for May 2010.

Galaxies and Starbursts

Witnessing the Formation of a Brightest Cluster Galaxy in a Nearby X-ray Cluster
Jesper Rasmussen, John S. Mulchaey, Lei Bai, Trevor J. Ponman, Somak Raychaudhury, Ali Dariush, arXiv:1005.3538 [pdf, ps, other]
Comments: 16 pages, 12 figures. ApJ accepted

UV+IR Star Formation Rates: Hickson Compact Groups with Swift and Spitzer
P. Tzanavaris, A. E. Hornschemeier, S. C. Gallagher, K. E. Johnson, C. Gronwall, S. Immler, A. E. Reines, E. Hoversten, J. C. Charlton, arXiv:1005.4059 [pdf, ps, other]
Comments: Accepted by ApJ. [8 Tables, 16 Figures. Color figures have reduced size for ArXiv - emulateapj v. 2/16/10]
Journal-ref: Astrophysical Journal 716 (2010) 556-573

From their abstract: "We present Swift UVOT (1600-3000A) 3-band photometry for 41 galaxies in 11 nearby (<4500km/s) Hickson Compact Groups (HCGs) of galaxies. We use the uvw2-band (2000A) to estimate the dust-unobscured component, SFR_UV, of the total star-formation rate, SFR_T. We use Spitzer MIPS 24-micron photometry to estimate SFR_IR, the dust-obscured component of SFR_T. We obtain SFR_T=SFR_UV+SFR_IR. Using 2MASS K_s band based stellar mass, M*, estimates, we calculate specific SFRs, SSFR=SFR_T/M*. SSFR values show a clear and significant bimodality, with a gap between low (<~3.2x10^-11 / yr) and high SSFR (>~1.2x10^-10 / yr) systems. All galaxies with MIR activity index a_IRAC <= 0 (>0) are in the high- (low-) SSFR locus, as expected if high levels of star-formation power MIR emission from polycyclic aromatic hydrocarbon molecules and a hot dust continuum. All elliptical/S0 galaxies are in the low-SSFR locus, while 22 out of 24 spirals/irregulars are in the high-SSFR locus, with two borderline cases. ... Unlike HCG galaxies, galaxies in a comparison quiescent SINGS sub-sample are continuously distributed both in SSFR and a_IRAC. Any uncertainties can only further enhance the SSFR bimodality. These results suggest that an environment characterized by high galaxy number-densities and low galaxy velocity-dispersions, such as the one found in compact groups, plays a key role in accelerating galaxy evolution by enhancing star-formation processes in galaxies and favoring a fast transition to quiescence."

Radiation pressure from massive star clusters as a launching mechanism for super-galactic winds
Norman Murray, Brice Ménard, Todd A. Thompson, arXiv:1005.4419 [pdf, ps, other]
Comments: Submitted to ApJ, comments welcome
Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); Galaxy Astrophysics (astro-ph.GA)

Their abstact: "Galactic outflows of low ionization, cool gas are ubiquitous in local starburst galaxies, and in the majority of galaxies at high redshift. How these cool outflows arise is still in question. Hot gas from supernovae has long been suspected as the primary driver, but this mechanism suffers from its tendency to destroy the cool gas as the latter is accelerated. We propose a modification of the supernova scenario that overcomes this difficulty.
Star formation is observed to take place in clusters; in a given galaxy, the bulk of the star formation is found in the ~20 most massive clusters. We show that, for L* galaxies, the radiation pressure from clusters with M>10^6 M_sun is able to expel the surrounding gas at velocities in excess of the circular velocity of the disk galaxy. This cool gas can travel above the galactic disk in less than 2 Myr, well before any supernovae erupt in the driving cluster. Once above the disk, the cool outflowing gas is exposed to radiation, and supernovae induced hot gas outflows, from other clusters in the disk, which drive it to distances of several tens to hundreds of kpc. Because the radiatively driven clouds grow in size as they travel, and because the hot gas is more dilute at large distance, the clouds are less subject to destruction if they do eventually encounter hot gas. Therefore, unlike wind driven clouds, radiatively driven clouds can survive to distances ~50 kpc. We identify these cluster-driven winds with large-scale galactic outflows. Another implication of our model is that only starburst galaxies, where massive clusters reside, are able to drive winds cold outflows on galactic scales via this mechanism. We find that the critical star formation rates above which large scale cool outflows will be launched to be ~0.1 M_sun/yr/kpc^2, which is in good agreement with observations."

I can see a quite a few problems with this line of argumentation. Hopefully I'll get around to addressing them in the monster paper I'm still adding to. Why write three papers when you can just write one absurdly large one?

Black Holes and AGN

"Comets" orbiting a black hole
R. Maiolino, G. Risaliti, M. Salvati, P. Pietrini, G. Torricelli-Ciamponi, M. Elvis, G. Fabbiano, V. Braito, J. Reeves, arXiv:1005.3365 [pdf, ps, other]
Comments: Accepted for publication in A&A. 11 pages, 9 figures

Their abstract: "We use a long (300 ksec), continuous Suzaku X-ray observation of the active nucleus in NGC1365 to investigate the structure of the circumnuclear BLR clouds through their occultation of the X-ray source. The variations of the absorbing column density and of the covering factor indicate that the clouds surrounding the black hole are far from having a spherical geometry (as sometimes assumed), instead they have a strongly elongated and cometary shape, with a dense head (n=10^11 cm^-3) and an expanding, dissolving tail. We infer that the cometary tails must be longer than a few times 10^13 cm and their opening angle must be smaller than a few degrees. We suggest that the cometary shape may be a common feature of BLR clouds in general, but which has been difficult to recognize observationally so far. The cometary shape may originate from shocks and hydrodynamical instabilities generated by the supersonic motion of the BLR clouds into the intracloud medium. As a consequence of the mass loss into their tail, we infer that the BLR clouds probably have a lifetime of only a few months, implying that they must be continuously replenished. We also find a large, puzzling discrepancy (two orders of magnitude) between the mass of the BLR inferred from the properties of the absorbing clouds and the mass of the BLR inferred from photoionization models; we discuss the possible solutions to this discrepancy."

Adaptive optics near infrared integral field spectroscopy of NGC 2992
S. Friedrich, R. I. Davies, E. K. S. Hicks, H. Engel, F. Müller-Sánchez, R. Genzel, L. J. Tacconi, arXiv:1005.4791 [pdf, ps, other]
Comments: 10 pages, 8 figures, accepted for publication in A&A

From their abstract: "NGC 2992 is an intermediate Seyfert 1 galaxy showing outflows on kilo parsec scales which might be due either to AGN or starburst activity. We therefore aim at investigating its central region for a putative starburst in the past and its connection to the AGN and the outflows. Observations were performed with the adaptive optics near infrared integral field spectrograph SINFONI on the VLT, complemented by longslit observations with ISAAC on the VLT, as well as N- and Q-band data from the Spitzer archive. The spatial and spectral resolutions of the SINFONI data are 50 pc and 83 km/s, respectively. ... A simple geometric model of two mutually inclined disks and an additional cone to describe an outflow was developed to explain the observed complex velocity field in H_2 1-0S(1). ... We find a starburst age of 40 Myr - 50 Myr from Br_gamma line diagnostics and the radio continuum; ongoing star formation can be excluded. Both the energetics and the timescales indicate that the outflows are driven by the AGN rather than the starburst. The complex velocity field observed in H_2 1-0S(1) in the central 450 pc can be explained by the superposition of the galaxy rotation and an outflow."

So, the questions remains - is there really an outflow on larger scales too?. The lack of clear cases of purely AGN-driven large scale winds really makes me doubt radiation-driven wind models.

Fading hard X-ray emission from the Galactic Centre molecular cloud Sgr B2
R. Terrier, G. Ponti, G. Belanger, A. Decourchelle, V. Tatischeff, A. Goldwurm, G. Trap, M. R. Morris, R. Warwick, arXiv:1005.4807 [pdf, ps, other]
Comments: Accepted for publication in ApJ. 10 pages, 5 figures

From their abstract: "The centre of our Galaxy harbours a 4 million solar mass black hole that is unusually quiet: its present X-ray luminosity is more than 10 orders of magnitude less than its Eddington luminosity. The observation of iron fluorescence and hard X-ray emission from some of the massive molecular clouds surrounding the Galactic Centre has been interpreted as an echo of a past flare. ... Here we report the observation of a clear decay of the hard X-ray emission from the molecular cloud Sgr B2 during the past 7 years thanks to more than 20 Ms of INTEGRAL exposure. The measured decay time is compatible with the light crossing time of the molecular cloud core . Such a short timescale rules out inverse bremsstrahlung by cosmic-ray ions as the origin of the X ray emission. We also obtained 2-100 keV broadband X-ray spectra by combining INTEGRAL and XMM-Newton data and compared them with detailed models of X-ray emission due to irradiation of molecular gas by (i) low-energy cosmic-ray electrons and (ii) hard X-rays. Both models can reproduce the data equally well, but the time variability constraints and the huge cosmic ray electron luminosity required to explain the observed hard X-ray emission strongly favor the scenario in which the diffuse emission of Sgr B2 is scattered and reprocessed radiation emitted in the past by Sgr A*. Using recent parallax measurements that place Sgr B2 in front of Sgr A*, we find that the period of intense activity of Sgr A* ended between 75 and 155 years ago."

Black Hole Mass, Host galaxy classification and AGN activity
Barry McKernan, K.E.Saavik Ford, Chris Reynolds, arXiv:1005.4907 [pdf, ps, other]
Comments: MNRAS accepted. 14 pages, 11 figures, complete Table 1 in online journal

Theoretical Cosmology

The intergalactic medium over the last 10 billion years I: Lyman alpha absorption and physical conditions
Romeel Davé, Benjamin D. Oppenheimer, Neal Katz, Juna A. Kollmeier, David H. Weinberg, arXiv:1005.2421 [pdf, ps, other]
Comments: 21 pages, submitted to MNRAS

Intergalactic Dust Extinction in Hydrodynamic Cosmological Simulations
Ying Zu, David H. Weinberg, Romeel Davé, Mark Fardal, Neal Katz, Dusan Keres, Benjamin D. Oppenheimer, arXiv:1005.4406 [pdf, ps, other]
Comments: 12 pages, 7 figures, to be submitted to MNRAS

Astrophysical Processes

Secondary ionization and heating by fast electrons
Steven R. Furlanetto and Samuel Johnson Stoever, 2010, MNRAS, 404, 1869
Full Text: HTML, PDF (Size: 720K)

Numerical Astrophysics and Computational Techniques

Searchable Sky Coverage of Astronomical Observations: Footprints and Exposures
Tamas Budavari, Alex Szalay, Gyorgy Fekete, arXiv:1005.2606 [pdf, other]
Comments: 11 pages, 7 figures, submitted to PASP

Their abstract: "Sky coverage is one of the most important pieces of information about astronomical observations. We discuss possible representations, and present algorithms to create and manipulate shapes consisting of generalized spherical polygons with arbitrary complexity and size on the celestial sphere. This shape specification integrates well with our Hierarchical Triangular Mesh indexing toolbox, whose performance and capabilities are enhanced by the advanced features presented here. Our portable implementation of the relevant spherical geometry routines comes with wrapper functions for database queries, which are currently being used within several scientific catalog archives including the Sloan Digital Sky Survey, the Galaxy Evolution Explorer and the Hubble Legacy Archive projects as well as the Footprint Service of the Virtual Observatory."

The Role of Provenance Management in Accelerating the Rate of Astronomical Research
G. Bruce Berriman, Ewa Deelman, arXiv:1005.3358 [pdf, other]
Comments: 8 pages, 1 figure; Proceedings of Science, 2010

Their abstract: "The availability of vast quantities of data through electronic archives has transformed astronomical research. It has also enabled the creation of new products, models and simulations, often from distributed input data and models, that are themselves made electronically available. These products will only provide maximal long-term value to astronomers when accompanied by records of their provenance; that is, records of the data and processes used in the creation of such products. We use the creation of image mosaics with the Montage grid-enabled mosaic engine to emphasize the necessity of provenance management and to understand the science requirements that higher-level products impose on provenance management technologies. We describe experiments with one technology, the "Provenance Aware Service Oriented Architecture" (PASOA), that stores provenance information at each step in the computation of a mosaic. The results inform the technical specifications of provenance management systems, including the need for extensible systems built on common standards. Finally, we describe examples of provenance management technology emerging from the fields of geophysics and oceanography that have applicability to astronomy applications."

Montage: a grid portal and software toolkit for science-grade astronomical image mosaicking
Joseph C. Jacob, et al, arXiv:1005.4454 [pdf, other]
Comments: 16 pages, 11 figures
Journal-ref: Int. J. Computational Science and Engineering. 2009

Their abstract: "Montage is a portable software toolkit for constructing custom, science-grade mosaics by composing multiple astronomical images. The mosaics constructed by Montage preserve the astrometry (position) and photometry (intensity) of the sources in the input images. The mosaic to be constructed is specified by the user in terms of a set of parameters, including dataset and wavelength to be used, location and size on the sky, coordinate system and projection, and spatial sampling rate. Many astronomical datasets are massive, and are stored in distributed archives that are, in most cases, remote with respect to the available computational resources. Montage can be run on both single- and multi-processor computers, including clusters and grids. Standard grid tools are used to run Montage in the case where the data or computers used to construct a mosaic are located remotely on the Internet. This paper describes the architecture, algorithms, and usage of Montage as both a software toolkit and as a grid portal. Timing results are provided to show how Montage performance scales with number of processors on a cluster computer. In addition, we compare the performance of two methods of running Montage in parallel on a grid."

Stars, Supernovae and Planets

Who Pulled the Trigger: a Supernova or an AGB Star?
Alan P. Boss, Sandra A. Keiser, arXiv:1005.3981 [pdf, ps, other]
Comments: 14 pages, 4 figures, 1 table, Astrophysical Journal Letters, in press

Their abstract: "The short-lived radioisotope $^{60}$Fe requires production in a core collapse supernova or AGB star immediately before its incorporation into the earliest solar system solids. Shock waves from a somewhat distant supernova, or a relatively nearby AGB star, have the right speeds to simultaneously trigger the collapse of a dense molecular cloud core and to inject shock wave material into the resulting protostar. A new set of FLASH2.5 adaptive mesh refinement hydrodynamical models shows that the injection efficiency depends sensitively on the assumed shock thickness and density. Supernova shock waves appear to be thin enough to inject the amount of shock wave material necessary to match the short-lived radioisotope abundances measured for primitive meteorites. Planetary nebula shock waves from AGB stars, however, appear to be too thick to achieve the required injection efficiencies. These models imply that a supernova pulled the trigger that led to the formation of our solar system. "

Herschel Observations of the W43 "mini-starburst"
J. Bally, et al, arXiv:1005.4092 [pdf, ps, other]
Comments: 5 pages, 3 figures, accepted for A&A Special Issue

From their abstract: "Aims: To explore the infrared and radio properties of one of the closest Galactic starburst regions. Methods: Images obtained with the Herschel Space Observatory at wavelengths of 70, 160, 250, 350, and 500 microns using the PACS and SPIRE arrays are analyzed and compared with radio continuum VLA data and 8 micron images from the Spitzer Space Telescope. ... Results: The W43 star-forming complex is resolved into a dense cluster of protostars, infrared dark clouds, and ridges of warm dust heated by massive stars. The 4 brightest compact sources with L > 1.5 x 10^4 Lsun embedded within the Z-shaped ridge of bright dust emission in W43 remain single at 4" (0.1 pc) resolution. These objects, likely to be massive protostars or compact clusters in early stages of evolution are embedded in clumps with masses of 10^3 to 10^4 Msun, but contribute only 2% to the 3.6 x 10^6 Lsun far-IR luminosity of W43 measured in a 16 by 16 pc box. The total mass of gas derived from the far-IR dust emission inside this region is ~10^6 Msun. Cometary dust clouds, compact 6 cm radio sources, and warm dust mark the locations of older populations of massive stars. Energy release has created a cavity blowing-out below the Galactic plane."

I wish people would stop calling individual star forming regions, even the biggest ones, starbursts. The term starburst has historically been used to denote significantly enhanced star formation at a galactic scale, and makes most sense when used thusly. See, e.g. Heckman, T., 2005, A&SS, 329, 3.

Evolution of massive stars with pulsation-driven superwinds during the RSG phase
Sung-Chul Yoon, Matteo Cantiello, arXiv:1005.4925 [pdf, ps, other]
Comments: Accepted for publications in ApJ Letters

Interesting to note the significance of pulsation in driving these winds. They're not just steady dust-driven winds. Are there any cases of steady dust-driven winds?

3-D supernovae and CP violation

2010-05-18T15:19:00.003-04:00

Some cool science news:

1. New simulations of supernova explosions by Müller's group at MPIA show significant differences in behaviour from previous antisymmetric 2-D simulations (MPIA press release, which is also the source of the image shown on the right).

The new computer models of the team at the Max Planck Institute for Astrophysics can now for the first time simulate the complete burst in all three dimensions, from the first milliseconds after the explosion is triggered in the core to a time three hours later, when the shock breaks out of the progenitor star. "We found substantial deviations in our 3D models compared to previous work in 2D," says Nicolay Hammer, the lead author of the paper, "especially the growth of instabilities and the propagation of clumps differ. These are not just minor variations; this effect determines the long-time evolution and ultimately the extent of mixing and observable appearance of core-collapse supernovae."

In the 3D-simulations, metal-rich clumps have much higher velocities than in the 2D case. These "bullets" expand much more rapidly, overtaking material from the outer layers. "With a simple analytic model we could demonstrate that the different geometry of the bullets, toroidal versus quasi-spherical, can explain the differences observed in our simulations," explains co-author Thomas Janka. "While we think that the differences between the 2D- and 3D-models that we found are probably generic, many features will depend strongly on the structure of the progenitor star, the overall energy and the initial asymmetry of the blast."

"We hope that our models, in comparison to observations, will help us to understand how stellar explosions start and what causes them", adds Ewald Müller, the third author of the paper. Investigating a wider variety of progenitor stars and initial conditions will therefore be the focus of future simulation work. In particular, a detailed model that reproduces all observational features of SN 1987A still remains a challenge.

Neat. May also have implications for superwinds, as there again we have a case of the acceleration and motion of dense clumps.

2. The DZero collaboration have found evidence for a 1%-level matter/anti-matter asymmetry (Fermilab press release)., i.e. much larger than previous examples of CP violation.

Interesting Astrophysics: May 03 to May 14

2010-05-14T09:14:00.002-04:00

It looks like the Herschel folks have been busy, judged by the deluge of preprints that have appeared on arXiv over the last few weeks. I found Roussel et al's paper on dust in/around M82 and Fischer et al's paper on Markarian 231 (and its molecular outflow) of particular interest.

Nevertheless X-ray-related papers dominate this issue of Interesting Astrophysics, from hot gas in galaxy halos (Mulchaey & Jeltema; Henley et al; Crain et al) to the detection or modelling of the Warm/Hot Intergalactic Medium (Yao et al; Cen & Chisari).

Galaxies and Starbursts

SPIRE imaging of M82: cool dust in the wind and tidal streams
H. Roussel, et al, arXiv:1005.1526 [pdf, ps, other]
Comments: accepted in A&A Herschel special issue

Their abstract in full: "M82 is a unique representative of a whole class of galaxies, starbursts with superwinds, in the Very Nearby Galaxy Survey with Herschel. In addition, its interaction with the M81 group has stripped a significant portion of its interstellar medium from its disk. SPIRE maps now afford better characterization of the far-infrared emission from cool dust outside the disk, and sketch a far more complete picture of its mass distribution and energetics than previously possible. They show emission coincident in projection with the starburst wind and in a large halo, much more extended than the PAH band emission seen with Spitzer. Some complex substructures coincide with the brightest PAH filaments, and others with tidal streams seen in atomic hydrogen. We subtract the far-infrared emission of the starburst and underlying disk from the maps, and derive spatially-resolved far-infrared colors for the wind and halo. We interpret the results in terms of dust mass, dust temperature, and global physical conditions. In particular, we examine variations in the dust physical properties as a function of distance from the center and the wind polar axis, and conclude that more than two thirds of the extraplanar dust has been removed by tidal interaction, and not entrained by the starburst wind."

The Stellar Kinematic Center and the True Galactic Nucleus of NGC253
F. Müller-Sánchez, O. González-Martín, J. A. Fernández-Ontiveros, J. A. Acosta-Pulido, M. A. Prieto, arXiv:1005.1645 [pdf, ps, other]

Comments: 33 pages, 7 figures, Accepted for publication in ApJ, Version with high resolution figures available at this http URL

Herschel PACS Spectroscopic Diagnostics of Local ULIRGs: Conditions and Kinematics in Mrk 231
Jacqueline Fischer, et al, arXiv:1005.2213 [pdf, other]
Comments: Accepted for publication in the Astronomy and Astrophysics Herschel Special Issue, 5 pages, 4 figures

Full abstract, emphasis mine: "In this first paper on the results of our Herschel PACS survey of local Ultraluminous Infrared Galaxies (ULIRGs), as part of our SHINING survey of local galaxies, we present far-infrared spectroscopy of Mrk 231, the most luminous of the local ULIRGs, and a type 1 broad absorption line AGN. For the first time in a ULIRG, all observed far-infrared fine-structure lines in the PACS range were detected and all were found to be deficient relative to the far infrared luminosity by 1 - 2 orders of magnitude compared with lower luminosity galaxies. The deficits are similar to those for the mid-infrared lines, with the most deficient lines showing high ionization potentials. Aged starbursts may account for part of the deficits, but partial covering of the highest excitation AGN powered regions may explain the remaining line deficits. A massive molecular outflow, discovered in OH and 18OH, showing outflow velocities out to at least 1400 km/sec, is a unique signature of the clearing out of the molecular disk that formed by dissipative collapse during the merger. The outflow is characterized by extremely high ratios of 18O / 16O suggestive of interstellar medium processing by advanced starbursts."

Hot Gas Halos in Early-Type Field Galaxies
John S. Mulchaey, Tesla E. Jeltema, arXiv:1004.5376 [pdf, ps, other]
Comments: Accepted for publication in ApJ Letters

Their abstract: "We use Chandra and XMM-Newton to study the hot gas content in a sample of field early-type galaxies. We find that the L_X-L_K relationship is steeper for field galaxies than for comparable galaxies in groups and clusters. The low hot gas content of field galaxies with L_K < L_star suggests that internal processes such as supernovae driven winds or AGN feedback expel hot gas from low mass galaxies. Such mechanisms may be less effective in groups and clusters where the presence of an intragroup or intracluster medium can confine outflowing material. In addition, galaxies in groups and clusters may be able to accrete gas from the ambient medium. While there is a population of L_K < L_star galaxies in groups and clusters that retain hot gas halos, some galaxies in these rich environments, including brighter galaxies, are largely devoid of hot gas. In these cases, the hot gas halos have likely been removed via ram pressure stripping. This suggests a very complex interplay between the intragroup/intracluster medium and hot gas halos of galaxies in rich environments with the ambient medium helping to confine or even enhance the halos in some cases and acting to remove gas in others. In contrast, the hot gas content of more isolated galaxies is largely a function of the mass of the galaxy, with more massive galaxies able to maintain their halos, while in lower mass systems the hot gas escapes in outflowing winds."

A fundamental relation between mass, SFR and metallicity in local and high redshift galaxies
F. Mannucci, G. Cresci, R. Maiolino, A. Marconi, A. Gnerucci, arXiv:1005.0006 [pdf, other]
Comments: 13 pages, submitted to MNRAS
Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

Their abstract: "We show that the mass-metallicity relation observed in the local universe is due to a more general relation between stellar mass M*, gas-phase metallicity and SFR. Local galaxies define a tight surface in this 3D space, the Fundamental Metallicity Relation (FMR), with a small residual dispersion of ~0.05 dex in metallicity, i.e, ~12%. At low stellar mass, metallicity decreases sharply with increasing SFR, while at high stellar mass, metallicity does not depend on SFR. High redshift galaxies, up to z~2.5 are found to follow the same FMR defined by local SDSS galaxies, with no indication of evolution. The evolution of the mass-metallicity relation observed up to z=2.5 is due to the fact that galaxies with progressively higher SFRs, and therefore lower metallicities, are selected at increasing redshifts, sampling different parts of the same FMR. By introducing the new quantity mu_alpha=log(M*)-alpha log(SFR), with alpha=0.32, we define a projection of the FMR that minimizes the metallicity scatter of local galaxies. The same quantity also cancels out any redshift evolution up to z~2.5, i.e, all galaxies have the same range of values of mu_0.32. At z>2.5, evolution of about 0.6 dex off the FMR is observed, with high-redshift galaxies showing lower metallicities. The existence of the FMR can be explained by the interplay of infall of pristine gas and outflow of enriched material. The former effect is responsible for the dependence of metallicity with SFR and is the dominant effect at high-redshift, while the latter introduces the dependence on stellar mass and dominates at low redshift. The combination of these two effects, together with the Schmidt-Kennicutt law, explains the shape of the FMR and the role of mu_0.32. The small metallicity scatter around the FMR supports the smooth infall scenario of gas accretion in the local universe."

A fundamental plane for field star-forming galaxies
M.A. Lara-López, J. Cepa, A. Bongiovanni, A.M. Pérez García, A. Ederoclite, H. Castañeda, M. Fernández Lorenzo, M. Póvic, M. Sánchez-Portal, arXiv:1005.0509 [pdf, ps, other]
Comments: Submitted to A&A as a letter to the Editor on April 15, 2010. 4 pages, 4 Figures

Their abstract: "Star formation rate (SFR), metallicity and stellar mass are within the important parameters of star--forming galaxies that characterize their formation and evolution. They are known to be related to each other at low and high redshift in the mass--metallicity, mass--SFR, and metallicity--SFR relations. In this work we demonstrate the existence of a plane in the 3D space defined by the axes SFR [log(SFR)(M_sun yr^-1)], gas metallicity [12+log(O/H)], and stellar mass [log(M_star/M_sun)] of star-forming galaxies. We used star--forming galaxies from the "main galaxy sample" of the Sloan Digital Sky Survey--Data Release 7 (SDSS-DR7) in the redshift range 0.04 < z < 0.1 and r-magnitudes between 14.5 and 17.77. Metallicities, SFRs, and stellar masses were taken from the Max-Planck-Institute for Astrophysics-John Hopkins University (MPA-JHU) emission line analysis database. From a final sample of 44214 galaxies, we find for the first time a fundamental plane for field galaxies relating the SFR, gas metallicity, and stellar mass for star--forming galaxies in the local universe. One of the applications of this plane would be estimating stellar masses from SFR and metallicity. High redshift data from the literature at redshift ~2.2 and 3.5, do not show evidence for evolution in this fundamental plane."

Our Milky Way as a Pure-Disk Galaxy -- A Challenge for Galaxy Formation
Juntai Shen, R. Michael Rich, John Kormendy, Christian D. Howard, Roberto De Propris, Andrea Kunder, arXiv:1005.0385 [pdf, ps, other]
Comments: 5 pages; emulateapj format; submitted to ApJL

Massive star formation in Wolf-Rayet galaxies. V: Star formation rates, masses and the importance of galaxy interactions
Angel R. Lopez-Sanchez
Comments: 33 pages, 21 figures, accepted for publication by A&A

From the abstract: "We have performed a comprehensive analysis of a sample of 20 starburst galaxies, most of them classified as Wolf-Rayet galaxies. In this paper, the last of the series, we analyze the global properties of our galaxy sample using multiwavelength data (X-ray, FUV, optical, NIR, FIR, and radio). The agreement between our Ha-based SFR and those provided by indicators at other wavelengths is remarkable, but we consider that the new Ha-based calibration provided by Calzetti et al. (2007) should be preferred over older calibrations. The FUV-based SFR provides a powerful tool to analyze the star-formation activity in both global and local scales independently to the Ha emission. We provide empirical relationships between the ionized gas mass, neutral gas mass, dust mass, stellar mass, and dynamical mass with the B-luminosity. ... Considering all data, we found that 17 up to 20 galaxies are clearly interacting or merging with low-luminosity dwarf objects or HI clouds. We conclude that interactions do play a fundamental role in the triggering mechanism of the strong star-formation activity observed in dwarf starburst galaxies."

The Dearth of Chemically Enriched Warm-Hot Circumgalactic Gas
Y. Yao, Q. D. Wang, S. V. Penton, T. M. Tripp, J. M. Shull, J. T. Stocke, arXiv:1005.0923 [pdf, ps, other]
Comments: 10 pages, 7 figures, and 5 tables. Accepted for publication in the ApJ, June 2010 - 20 v716 issue.

Argues against a local group origin for the z~0 X-ray absorbers, as have others. Also "These results indicate that the putative CGM [Circum Galactic Medium] in the temperature range of 10^{5.5}-10^{6.3} K may not be able to account for the missing baryons unless the metallicity is less than 10% solar." Of course its probably more accurate to say the mire astronomers believe the missing baryons to be in the warm-hot inter galactic medium, and not within galactic halos at all.

The Origin of the Hot Gas in the Galactic Halo: Confronting Models with XMM-Newton Observations
David B. Henley, Robin L. Shelton, Kyujin Kwak, M. Ryan Joung, Mordecai-Mark Mac Low, arXiv:1005.1085 [pdf, ps, other]
Comments: 18 pages, 13 figures. Submitted to the Astrophysical Journal
Subjects: Galaxy Astrophysics (astro-ph.GA)

Full abstract: "We compare the predictions of three physical models for the origin of the hot halo gas with the observed halo X-ray emission, derived from 26 high-latitude XMM-Newton observations of the soft X-ray background between $l=120\degr$ and $l=240\degr$. These observations were chosen from a much larger set of observations as they are expected to be the least contaminated by solar wind charge exchange emission. We characterize the halo emission in the XMM-Newton band with a single-temperature plasma model. We find that the observed halo temperature is fairly constant across the sky (~1.8e6-2.4e6 K), whereas the halo emission measure varies by an order of magnitude ($\sim$0.0005-0.006 cm^-6 pc), including significant sightline-to-sightline variation on scales as small as a few degrees. When we compare our observations with the model predictions, we find that most of the hot gas observed with XMM-Newton does not reside in an extended hot halo (predicted by disk galaxy formation models), nor is it contained within isolated extraplanar supernova remnants - both these models are at least an order of magnitude too faint in the XMM-Newton band. A model of a supernova-driven interstellar medium, one feature of which is a fountain of hot gas from the disk into the halo, gives the best agreement with the observed 0.4-2.0 keV surface brightness. This model overpredicts the halo X-ray temperature by a factor of ~2. However, there are a several plausible explanations for this discrepancy. Therefore, our general conclusion is that the hot halo gas observed with XMM-Newton originates in a fountain driven into the halo by disk supernovae."

Can galaxy outflows and re-accretion produce a downsizing in the specific star-formation rate of late-type galaxies?
C. Firmani, V. Avila-Reese and A. Rodríguez-Puebla, 2010, MNRAS, 404, 1100
Full Text: HTML, PDF (Size: 685K)

Theoretical Cosmology

Star Formation Feedback and Metal Enrichment History Of The Intergalactic Medium
Renyue Cen, Nora Elisa Chisari, arXiv:1005.1451 [pdf, other]
Comments: 52 pages, 26 figures, submitted to ApJ, all comments welcome

From their abstract: "Using the state-of-the-art cosmological hydrodynamic simulations we compute the metal enrichment history of the intergalactic medium (IGM). Overall, we show that galactic superwind feedback from star formation is able to transport metals to the IGM that matches a broad range of observations. We find ... (6) While gravitational shocks from large-scale structure formation dominate the energy budget (80-90%) for turning about 50% of IGM to the warm-hot intergalactic medium (WHIM) by z=0, galactic superwind feedback shocks are energetically dominant over gravitational shocks at z>1-2. (7) Most of the so-called "missing metals" at z=2-3 are hidden in a warm-hot (T=10^{4.5-7}K) gaseous phase. (8) Approximately (37,46,10,7)% of the total metals at z=0 are in (stars, WHIM, X-ray gas, cold gas); the distribution stands at (23,57,2,18)% and (14,51,4,31)% at z=2 and z=4, respectively."

X-ray coronae in simulations of disc galaxy formation
Robert A. Crain, Ian G. McCarthy, Carlos S. Frenk, Tom Theuns, Joop Schaye, arXiv:1005.1642 [pdf, other]

Comments: 21 pages, 16 figures. Accepted for publication in MNRAS. Accompanying visualisations at this http URL

Their abstract: "The existence of X-ray luminous gaseous coronae around massive disc galaxies is a long-standing prediction of galaxy formation theory in the cold dark matter cosmogony. This prediction has garnered little observational support, with non-detections commonplace and detections for only a relatively small number of galaxies which are much less luminous than expected. We investigate the coronal properties of a large sample of bright, disc-dominated galaxies extracted from the GIMIC suite of cosmological hydrodynamic simulations recently presented by Crain et al. Remarkably, the simulations reproduce the observed scalings of X-ray luminosity with K-band luminosity and star formation rate and, when account is taken of the density structure of the halo, with disc rotation velocity as well. Most of the star formation in the simulated galaxies (which have realistic stellar mass fractions) is fuelled by gas cooling from a quasi-hydrostatic hot corona. However, these coronae are more diffuse, and of a lower luminosity, than predicted by the analytic models of White & Frenk because of a substantial increase in entropy at z ~ 1-3. Both the removal of low entropy gas by star formation and energy injection from supernovae contribute to this increase in entropy, but the latter is dominant for halo masses M_200 <~ 10^(12.5) Msun. Only a small fraction of the mass of the hot gas is outflowing as a wind but, because of its high density and metallicity, it contributes disproportionally to the X-ray emission. The bulk of the X-ray emission, however, comes from the diffuse quasi-hydrostatic corona which supplies the fuel for ongoing star formation in discs today. Future deep X-ray observations with high spectral resolution (e.g. with NeXT/ASTRO-H or IXO) should be able to map the velocity structure of the hot gas and test this fundamental prediction of current galaxy formation theory."

Numerical Astrophysics

Multi-layered configurations in differentially-rotational equilibrium
Kenta Kiuchi, Hiroki Nagakura, Shoichi Yamada, arXiv:1005.2236 [pdf, ps, other]
Comments: To appear on APJ, high-resolution figures are available in the published version.

Full abstract: "We present a new formula to numerically construct configurations in rotational equilibrium, which consist of multiple layers. Each layer rotates uniformly or differentially according to cylindrical rotation-laws that are different from layer to layer. Assuming a different barotropic equation of state (EOS) for each layer, we solve the Bernoulli equation in each layer separately and combine the solutions by imposing continuity of the pressure at each boundary of the layers. It is confirmed that a single continuous barotropic EOS is incompatible with the junction condition. Identifying appropriate variables to be solved, we construct a convergent iteration scheme. For demonstration, we obtain two-layered configurations, each layer of which rotates rapidly with either an "$\Omega$-constant law" or a "$j$-constant law" or a "$v$-constant law". Other rotation laws and/or a larger number of layers can be treated similarly. We hope that this formula will be useful in studying the stellar evolution in multi-dimension with the non-spherical configuration induced by rotation being fully taken into account."

Stars, Supernovae and Planets

On the evolution of a star cluster and its multiple stellar systems following gas dispersal
Nickolas Moeckel and Matthew R. Bate, 2010, MNRAS, 404, 712
Full Text: HTML, PDF (Size: 3726K)

Bursting SN 1996cr's Bubble: Hydrodynamic and X-ray Modeling of its Circumstellar Medium
Vikram V. Dwarkadas, Daniel Dewey, Franz Bauer, arXiv:1005.1090 [pdf, ps, other]
Comments: Accepted to MNRAS. 21 pages, 8 Figures, 6 in color. For a version with higher resolution colour figures see this http URL
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

From their abstract: "SN1996cr is one of the five closest SNe to explode in the past 30 years. Due to its fortuitous location in the Circinus Galaxy at ~ 3.7 Mpc, there is a wealth of recently acquired and serendipitous archival data available to piece together its evolution over the past decade, including a recent 485 ks Chandra HETG spectrum. In order to interpret this data, we have explored hydrodynamic simulations, followed by computations of simulated spectra and light curves under non-equilibrium ionization conditions, and directly compared them to the observations. Our simulated spectra manage to fit both the X-ray continuum and lines at 4 epochs satisfactorily, while our computed light curves are in good agreement with additional flux-monitoring data sets. These calculations allow us to infer the nature and structure of the circumstellar medium, the evolution of the SN shock wave, and the abundances of the ejecta and surrounding medium. The data imply that SN 1996cr exploded in a low-density medium before interacting with a dense shell of material about 0.03pc away from the progenitor star."

Radio and X-ray Observations of the Type Ic SN 2007gr Reveal an Ordinary, Non-relativistic Explosion
Alicia M. Soderberg, Andreas Brunthaler, Ehud Nakar, Roger A. Chevalier, arXiv:1005.1932 [pdf, ps, other]
Comments: 14 pages, 6 figures, submitted to ApJ

Again, evidence that the supernova blastwave is expanding into circum-stellar medium shaped by stellar winds.

Generation of radiative knots in a randomly pulsed protostellar jet II. X-ray emission
R. Bonito, S. Orlando, M. Miceli, J. Eislöffel, G. Peres, F. Favata, arXiv:1005.2125 [pdf, ps, other]
Comments: Accepted for publication in Astronomy and Astrophysics

Their abstract: "Protostellar jets are known to emit in a wide range of bands, from radio to IR to optical bands, and to date also about ten X-ray emitting jets have been detected, with a rate of discovery of about one per year. We aim at investigating the mechanism leading to the X-ray emission detected in protostellar jets and at constraining the physical parameters that describe the jet/ambient interaction by comparing our model predictions with observations. We perform 2D axisymmetric hydrodynamic simulations of the interaction between a supersonic jet and the ambient. The jet is described as a train of plasma blobs randomly ejected by the stellar source along the jet axis. We explore the parameter space by varying the ejection rate, the initial jet Mach number, and the initial density contrast between the ambient and the jet. We synthesized from the model the X-ray emission as it would be observed with the current X-ray telescopes. The mutual interactions among the ejected blobs and of the blobs with the ambient medium lead to complex X-ray emitting structures within the jet: irregular chains of knots; isolated knots with measurable proper motion; apparently stationary knots; reverse shocks. The predicted X-ray luminosity strongly depends on the ejection rate and on the initial density contrast between the ambient and the jet, with a weaker dependence on the jet Mach number. Our model represents the first attempt to describe the X-ray properties of all the X-ray emitting protostellar jets. The comparison between our model predictions and the observations can provide a useful diagnostic tool necessary for a proper interpretation of the observations. In particular, we suggest that the observable quantities derived from the spectral analysis of X-ray observations can be used to constrain the ejection rate, a parameter explored in our model that is not measurable by current observations."

Problems with SALT

2010-05-03T16:00:00.003-04:00

SciAm online has a short article discussing SALT's (Southern African Large Telescope) ongoing problems with spherical aberration: "Southern Hemisphere's Largest Telescope Hamstrung by Optical Problems" by Bruce Dorminey.

[Image: SALT's 11 meter diameter segmented primary mirror. From the SALT website telescope overview.]

Interesting Astrophysics: Apr 19 to Apr 30

2010-04-30T09:20:00.002-04:00

There really haven't been many papers or preprints that have caught my eye over the last two weeks or so, so this edition of Interesting Astrophysics is pretty short. The most interesting (to me) of the bunch are Nobukawa et al - on origin of K shell X-ray line emission in the Galactic Center - and Parkin & Pittard's work on the effects of numerical heat conduction on the dynamics of colliding winds.

Galaxies and Starbursts

The Buried Starburst in the Interacting Galaxy II Zw 096 as Revealed by the Spitzer Space Telescope
Hanae Inami, et al, arXiv:1004.3543 [pdf, ps, other]
Comments: 46 pages, 10 figures, accepted for publication in AJ

Discovery of K-Shell Emission Lines of Neutral Atoms in the Galactic Center Region
Masayoshi Nobukawa, Katsuji Koyama, Takeshi Go Tsuru, Syukyo G Ryu, Vincent Tatischeff, arXiv:1004.3891 [pdf, ps, other]
Comments: 7 pages, 5 figures, accepted for publication in PASJ (Vol.62, No.2, pp.423--429)

This is potentially important. If the interpretation is correct then we don't have to worry so much about unusual (non-Maxwellian) electron energy distributions creating exotic X-ray spectra, and can also still trust and use more traditional models/processes in interpreting diffuse X-ray emission in galaxies other than the Milky Way. This comes at the price of invoking an explanation that posits substantially higher X-ray luminosities for the Milky Way's central black hole in the past than is observed now.

Their abstract: "The K-shell emission line of neutral irons from the Galactic center (GC) region is one of the key for the structure and activity of the GC. The origin is still open question, but possibly due either to X-ray radiation or to electron bombarding to neutral atoms. To address this issue, we analyzed the Suzaku X-ray spectrum from the GC region of intense neutral iron line emission, and report on the discovery of Kalpha lines of neutral argon, calcium, chrome, and manganese atoms. The equivalent widths of these Kalpha lines indicate that the metal abundances in the GC region should be ~1.6 and ~4 of solar value, depending on the X-ray and the electron origins, respectively. On the other hand, the metal abundances in the hot plasma in the GC region are found to be ~1-2 solar. These results favor that the origin of the neutral Kalpha lines are due to X-ray irradiation."

Note that what they observe is K-alpha emission from neutral Fe, Ar, Ca, Mg and Chrome(!). This is unlike M82 (Griffiths et al 2000, Strickland & Heckman 2007, 2009), where we see Helium-like emission from S, Ar, Ca and Fe, i.e. direct emission from highly ionized gas, not X-ray fluorescence from irradiated neutral atoms.

Relating dust, gas and the rate of star formation in M31
F. S. Tabatabaei, E. M. Berkhuijsen, arXiv:1004.4306 [pdf, ps, other]
Comments: 22 pages accepted for publication in A&A

Black Holes and AGN

X-ray and multiwavelength view of NGC 4278. A LINER-Seyfert connection?

G. Younes, D. Porquet, B. Sabra, N. Grosso, J.N. Reeves, M.G. Allen, arXiv:1004.5134 [pdf, other]

Comments: 14 pages, 15 figures, accepted for publication in Astronomy and Astrophysics

Mid-Infrared Properties of the Swift Burst Alert Telescope Active Galactic Nuclei Sample of the Local Universe. I. Emission-Line Diagnostics
K. A. Weaver, M. Meléndez, R. F. Mushotzky, S. Kraemer, K. Engle, E. Malumuth, J. Tueller, C. Markwardt, C.T. Berghea, R. P. Dudik, L. M. Winter, L. Armus, arXiv:1004.5321 [pdf, ps, other]
Comments: 54 pages, 9 Figures. Accepted for publication in The Astrophysical Journal.

Numerical Astrophysics and Hydrodynamics

Numerical heat conduction in hydrodynamical models of colliding hypersonic flows
E. R. Parkin, J. M. Pittard, arXiv:1004.3753 [pdf, ps, other]
Comments: 14 pages, 10 figures, accepted for publication in MNRAS

Their abstract: "Hydrodynamical models of colliding hypersonic flows are presented which explore the dependence of the resulting dynamics and the characteristics of the derived X-ray emission on numerical conduction and viscosity. For the purpose of our investigation we present models of colliding flow with plane-parallel and cylindrical divergence. Numerical conduction causes erroneous heating of gas across the contact discontinuity which has implications for the rate at which the gas cools. We find that the dynamics of the shocked gas and the resulting X-ray emission are strongly dependent on the contrast in the density and temperature either side of the contact discontinuity, these effects being strongest where the postshock gas of one flow behaves quasi-adiabatically while the postshock gas of the other flow is strongly radiative. Introducing additional numerical viscosity into the simulations has the effect of damping the growth of instabilities, which in some cases act to increase the volume of shocked gas and can re-heat gas via sub-shocks as it flows downstream. The resulting reduction in the surface area between adjacent flows, and therefore of the amount of numerical conduction, leads to a commensurate reduction in spurious X-ray emission, though the dynamics of the collision are compromised. The simulation resolution also affects the degree of numerical conduction. A finer resolution better resolves the interfaces of high density and temperature contrast and although numerical conduction still exists the volume of affected gas is considerably reduced. However, since it is not always practical to increase the resolution, it is imperative that the degree of numerical conduction is understood so that inaccurate interpretations can be avoided. This work has implications for the dynamics and emission from astrophysical phenomena which involve high Mach number shocks."

Prompt Global Strike

2010-04-23T09:19:00.002-04:00

The NYT has an interesting article about a new weapon system.

WASHINGTON — In coming years, President Obama will decide whether to deploy a new class of weapons capable of reaching any corner of the earth from the United States in under an hour and with such accuracy and force that they would greatly diminish America’s reliance on its nuclear arsenal.

Yet even now, concerns about the technology are so strong that the Obama administration has acceded to a demand by Russia that the United States decommission one nuclear missile for every one of these conventional weapons fielded by the Pentagon. That provision, the White House said, is buried deep inside the New Start treaty that Mr. Obama and President Dmitri A. Medvedev signed in Prague two weeks ago.

Initially I thought this was a pure kinetic energy weapon, but on closer reading its a very large "conventional warhead." The hypersonic glider is very cool though.

Microquasar in M82?

2010-04-16T09:43:00.002-04:00

I'm seeing this story all over the Internet. Sadly I don't have time to make much comment on it.

The hard working and often sadly under-appreciated folks at Jodrell Bank have made a splash with news of the sudden appearance of a mysterious radio source (woo!) in M82, which is possibly a microquasar (e.g. like SS 433 in our own Galaxy. *). The official Jodrell Bank press release is definitely the best place to get the background on this exciting discovery, as the press stories tend to be... superficial.

It is unfortunate that the images used in all the press stories I've seen so far, and even the lead image on the Jodrell Bank press release, are NOT actual radio images of M82, let alone images showing the new source, but either the Hubble ACS image (i.e. optical light) or a Spitzer image (near Infra-red light). This is the tyranny of Hubble - its a pretty picture machine, but very often the real science can't be done in the optical. Yet what mission does the public associate with astronomy and astrophysics... Hubble. If your mission or observatory doesn't make pretty pictures, or perish the thought, doesn't make images at all (e.g. FUSE) then you have a public relations problem, and potentially a funding problem.

(*) Sadly the wikipedia entry on SS 433 doesn't do a great job in conveying how interesting and awesome this object is.

Interesting Astrophysics: Apr 05 to Apr 16

2010-04-16T09:08:00.002-04:00

The last two weeks have produced quite a number of interesting papers and preprints. Given the diversity I'll let them speak for themselves. Note to self: two papers on cloud statistics.

Galaxies and Starbursts

An Empirical Characterization of Extended Cool Gas Around Galaxies Using MgII Absorption Features
Hsiao-Wen Chen, Jennifer E. Helsby, Jean-Rene Gauthier, Stephen A. Shectman, Ian B. Thompson, Jeremy L. Tinker, arXiv:1004.0705 [pdf, ps, other]

Comments: 20 pages, 13 figures; to appear in the Astrophysical Journal 2010 May 10 issue; a version with higher resolution figures can be found at this http URL

From their abstract: "... The lack of correlation between Wr(2796) and galaxy colors suggests a lack of physical connection between the origin of extended MgII halos and recent star formation history of the galaxies ..."

Seeing Through the Trough: Outflows and the Detectability of Lyman Alpha Emission from the First Galaxies
Mark Dijkstra, Stuart Wyithe, arXiv:1004.2490 [pdf, ps, other]
Comments: 11 pages, 7 figures, submitted to MNRAS

From their abstract: "In this paper we demonstrate that the radiative transfer effects in the interstellar medium (ISM), which cause Lya flux to emerge from galaxies at frequencies where the Gunn-Peterson optical depth is reduced, can substantially enhance the prospects for detection of the Lya line at high redshift. In particular, scattering off outflows of interstellar HI gas can modify the Lya spectral line shape such that >5% of the emitted Lya radiation is transmitted directly to the observer, even through a fully neutral IGM. It may therefore be possible to directly observe `strong' Lya emission lines (EW > 50 Angstrom rest frame) from the highest redshift galaxies that reside in the smallest HII `bubbles' early in the reionization era with JWST. In addition, we show that outflows can boost the fraction of Lya radiation that is transmitted through the IGM during the latter stages of reionization, and even post-reionization."

The Great Observatories All-Sky LIRG Survey: Comparison of Ultraviolet and Far-Infrared Properties
Justin H. Howell, et al, arXiv:1004.0985 [pdf, ps, other]
Comments: 37 pages, 10 figures, accepted for publication in ApJ

From their abstract: "The Great Observatories All-sky LIRG Survey (GOALS) consists of a complete sample of 202 Luminous Infrared Galaxies (LIRGs) selected from the IRAS Revised Bright Galaxy Sample (RBGS). The galaxies span the full range of interaction stages, from isolated galaxies to interacting pairs to late stage mergers. We present a comparison of the UV and infrared properties of 135 galaxies in GOALS observed by GALEX and Spitzer. For interacting galaxies with separations greater than the resolution of GALEX and Spitzer (2-6"), we assess the UV and IR properties of each galaxy individually. The contribution of the FUV to the measured SFR ranges from 0.2% to 17.9%, with a median of 2.8% and a mean of 4.0 +/- 0.4%. The specific star formation rate of the GOALS sample is extremely high, with a median value (3.9*10^{-10} yr^{-1}) that is comparable to the highest specific star formation rates seen in the Spitzer Infrared Nearby Galaxies Survey sample."

Dwarf-Galaxy Cosmology
Regina Schulte-Ladbeck, Ulrich Hopp, Elias Brinks, Andrey Kravtsov, arXiv:1004.1139 [pdf, other]
Comments: This is the editorial paper which introduces the Special Issue on Dwarf-Galaxy Cosmology published in Advances in Astronomy. The issue contains fourteen review papers, and one original research article. All papers were peer-reviewed by a minimum of two referees. To read the Special Issue, please follow this link: this http URL .

Their abstract: "Dwarf galaxies provide opportunities for drawing inferences about the processes in the early universe by observing our "cosmological backyard"-the Local Group and its vicinity. This special issue of the open-access journal Advances in Astronomy is a snapshot of the current state of the art of dwarf-galaxy cosmology."

Sadly no articles focussing on outflows or supernova feedback.

Comparing Ultraviolet and Infrared-Selected Starburst Galaxies in Dust Obscuration and Luminosity
Lusine A. Sargsyan, Daniel W. Weedman, James R. Houck, arXiv:1004.1551 [pdf, ps, other]
Comments: accepted for publication in The Astrophysical Journal

Concludes that the "obscuration corrections by factors of two to three determined from reddening of the ultraviolet continuum for Lyman Break Galaxies with z > 2 are insufficient, and should be at least a factor of 10 for M(UV) about -17, with decreasing correction for more luminous sources."

A Multi-wavelength analysis of M81: insight on the nature of Arp's loop
A. Sollima, A. Gil de Paz, D. Martinez-Delgado, R.J. Gabany, J. Gallego, T. Hallas, arXiv:1004.1610 [pdf, ps, other]
Comments: 7 pages, 7 figures, accepted for publication by A&A

Their abstract: "The optical ring like structure detected by Arp (1965) around M81 (commonly referenced as "Arp's loop") represents one of the most spectacular feature observed in nearby galaxies. Arp's loop is commonly interpreted as a tail resulting from the tidal interaction between M81 and M82. However, since its discovery the nature of this feature has remained controversial. Aims: Our primary purpose was to identify the sources of optical and infrared emission observed in Arp's loop. Methods: The morphology of the Arp's loop has been investigated with deep wide-field optical images. We also measured its colors using IRAS and Spitzer-MIPS infrared images and compared them with those of the disk of M81 and Galactic dust cirrus that fills the area where M81 is located. Results: Optical images reveal that this peculiar object has a filamentary structure characterized by many dust features overlapping M81's field. The ratios of far-infrared fluxes and the estimated dust-to-gas ratios indicate the infrared emission of Arp's loop is dominated by the contribution of cold dust that is most likely from Galactic cirrus. Conclusions: The above results suggest that the light observed at optical wavelengths is a combination of emission from i) a few recent star forming regions located close to M81, where both bright UV complexes and peaks in the HI distribution are found, ii) the extended disk of M81 and iii) scattered light from the same Galactic cirrus that is responsible for the bulk of the far infrared emission."

I've mentioned the Galactic cirrus emission along the line of sight to the M81/M82 group previously in this blog, as the cirrus is visible even in scattered optical/UV light. Amateur astronomers have termed this cirrus-associated nebulosity Integrated Flux Nebulae.

Black Holes and AGN

Momentum-driven winds and positive AGN feedback
Joe Silk, Adi Nusser, arXiv:1004.0857 [pdf, ps, other]
Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

Their abstract: "Force balance considerations put a limit on the rate of AGN radiation momentum output, $L/c$, capable of driving galactic superwinds. We show that this condition is insufficient: black holes obeying the observed $\mbh -\sigma $ relation cannot supply enough energy in radiation which can drive the gas out by pressure alone. The shortfall is by up to an order of magnitude in most, but not all, cases. We propose that outflow-triggering of star formation by enhancing the intercloud medium turbulent pressure and squeezing clouds can supply the necessary boost, and suggest possible tests of this hypothesis. We further point out that the time-scales for Bondi accretion and for orbital decay of merging clumps by dynamical friction in the nuclear disk around a central black hole both follow a similar scaling with mass, favoring the most massive black holes, but the latter process is up to two orders of magnitude more rapid at $z\gtsim 10.$ The combination of accretion and coalescence results in earlier formation of more massive black holes, and, in particular, can account for the masses of the black holes inferred to power AGN at $z\sim 6.$"

Molecular clouds: X-ray mirrors of the Galactic nuclear activity
Gabriele Ponti, Regis Terrier, Andrea Goldwurm, Guillaume Belanger, Guillaume Trap, arXiv:1004.1412 [pdf, ps, other]
Comments: 4 pages, "The Galactic Center: A Window on the Nuclear Environment of Disk Galaxies" ASP Conference Series, 2010 eds: M. Morris, D. Q. Wang and F. Yuan

Did the supermassive black hole that currently lurks quietly at the center of our Galaxy flare up about 100 years ago?

Interstellar Medium

The Mass-Size Relation from Clouds to Cores. II. Solar Neighborhood Clouds
Jens Kauffmann, Thushara Pillai, Rahul Shetty, Philip C. Myers, Alyssa A. Goodman, arXiv:1004.1170 [pdf, ps, other]
Comments: accepted to the Astrophysical Journal

I must read this more carefully.

Abstract in full: "We measure the mass and size of cloud fragments in several molecular clouds continuously over a wide range of spatial scales (0.05 < r / pc < 3). Based on the recently developed "dendrogram-technique", this characterizes dense cores as well as the enveloping clouds. "Larson's 3rd Law" of constant column density, m(r) = C*r^2, is not well suited to describe the derived mass-size data. Solar neighborhood clouds not forming massive stars (< 10 M_sun; Pipe Nebula, Taurus, Perseus, and Ophiuchus) obey m(r) < 870 M_sun (r / pc)^1.33 . In contrast to this, clouds forming massive stars (Orion A, G10.15$-$0.34, G11.11$-$0.12) do exceed the aforementioned relation. Thus, this limiting mass-size relation may approximate a threshold for the formation of massive stars. Across all clouds, cluster-forming cloud fragments are found to be---at given radius---more massive than fragments devoid of clusters. The cluster-bearing fragments are found to roughly obey a mass-size law m = C*r^1.27 (where the exponent is highly uncertain in any given cloud, but is certainly smaller than 1.5).

Physical Properties of Giant Molecular Clouds in the Large Magellanic Cloud
A. Hughes, et al, arXiv:1004.2094 [pdf, ps, other]
Comments: 28 pages, 10 figures, accepted by MNRAS

Searching for Diffuse Nonthermal X-Rays from the Superbubbles N11 and N51D in the Large Magellanic Cloud
H. Yamaguchi, M. Sawada, A. Bamba, arXiv:1004.0753 [pdf, ps, other]
Comments: 9 pages, accepted for publication in ApJ.

Their abstract (emphasis mine): "We report on observations of the superbubbles (SBs) N11 and N51D in the Large Magellanic Cloud (LMC) with Suzaku and XMM-Newton. The interior of both SBs exhibits diffuse X-ray emission, which is well represented by thin thermal plasma models with a temperature of 0.2-0.3keV. The presence of nonthermal emission, claimed in previous works, is much less evident in our careful investigation. The 3-sigma upper limits of 2-10keV flux are 3.6*10^{-14}ergs/cm^2/s and 4.7*10^{-14}ergs/cm^2/s for N11 and N51D, respectively. The previous claims of the detection of nonthermal emission are probably due to the inaccurate estimation of the non X-ray background. We conclude that no credible nonthermal emission has been detected from the SBs in the LMC, with the exception of 30 Dor C. "

Hydrodynamics and Numerical Astrophysics

A comparison between grid and particle methods on the statistics of driven, supersonic, isothermal turbulence
Daniel J. Price, Christoph Federrath, arXiv:1004.1446 [pdf, ps, other]

Comments: 16 pages, 15 figures, accepted to MNRAS. Associated movies, images and full res version at: this http URL

The Athena Astrophysical MHD Code in Cylindrical Geometry
Aaron Skinner, Eve Ostriker, arXiv:1004.2487 [pdf, ps, other]

Their abstract: "A method for implementing cylindrical coordinates in the Athena magnetohydrodynamics (MHD) code is described. The extension follows the approach of Athena's original developers and has been designed to alter the existing Cartesian-coordinates code as minimally and transparently as possible. The numerical equations in cylindrical coordinates are formulated to maintain consistency with constrained transport, a central feature of the Athena algorithm, while making use of previously implemented code modules such as the Riemann solvers. Angular-momentum transport, which is critical in astrophysical disk systems dominated by rotation, is treated carefully. We describe modifications for cylindrical coordinates of the higher-order spatial reconstruction and characteristic evolution steps as well as the finite-volume and constrained transport updates. Finally, we present a test suite of standard and novel problems in one-, two-, and three-dimensions designed to validate our algorithms and implementation and to be of use to other code developers. The code is suitable for use in a wide variety of astrophysical applications and is freely available for download on the web."

Instrumentation

The New Hard X-ray Mission
G. Tagliaferri, et al, arXiv:1004.2691 [pdf]
Comments: 9 pages, 5 figures. Accepted for publication on PoS, proceedings of "The Extreme sky: Sampling the Universe above 10 keV", held in Otranto (Italy), 13-17 October 2009

Their abstract: "The Italian New Hard X-ray Mission (NHXM) has been designed to provide a real breakthrough on a number of hot astrophysical issues that includes: black holes census, the physics of accretion, the particle acceleration mechanisms, the effects of radiative transfer in highly magnetized plasmas and strong gravitational fields. NHXM is an evolution of the HEXIT-Sat concept and it combines fine imaging capability up to 80 keV, today available only at E<10 keV, with sensitive photoelectric imaging polarimetry. It consists of four identical mirrors, with a 10 m focal length, achieved after launch by means of a deployable structure. Three of the four telescopes will have at their focus identical spectral-imaging cameras, while X-ray imaging polarimetric cameras will be placed at the focus of the fourth. In order to ensure a low and stable background, NHXM will be placed in a low Earth equatorial orbit. In this paper we provide an overall description of this mission that is currently in phase B."

Stars, Supernovae and Planets

One-sided Outflows/Jets from Rotating Stars with Complex Magnetic Fields
R.V.E. Lovelace, M.M. Romanova, G.V. Ustyugova, A.V. Koldoba, arXiv:1004.0385 [pdf, other]
Comments: 10 pages, 11 figures

Dusty Disks around White Dwarfs I: Origin of Debris Disks
Ruobing Dong, Yan Wang, D. N.C. Lin, X.-W. Liu, arXiv:1004.0696 [pdf, ps, other]
Comments: 38 pages, 7 figures, single column, accepted by ApJ

The NSF censors itself with an astrophysicist's help

2010-04-09T08:43:00.005-04:00

Wow, this story (reported in ScienceInsider by Yudhijit Bhattacharjee, "Evolution, Big Bang Polls Omitted From NSF Report") is a scandal.

In an unusual last-minute edit that has drawn flak from the White House and science educators, a federal advisory committee omitted data on Americans' knowledge of evolution and the big bang from a key report. The data shows that Americans are far less likely than the rest of the world to accept that humans evolved from earlier species and that the universe began with a big bang.

They're not surprising findings, but the National Science Board, which oversees the National Science Foundation (NSF), says it chose to leave the section out of the 2010 edition of the biennial Science and Engineering Indicators because the survey questions used to measure knowledge of the two topics force respondents to choose between factual knowledge and religious beliefs.

So the claim is that it is unfair to say people who reject evolution or the Big Bang are scientifically illiterate, as if to do so would somehow infringe their religious liberty. What utter nonsense. I'd almost be happier to believe the data was omitted because the terrible response rates are an embarrassment for this country.

The deleted text, obtained by ScienceInsider, does not differ radically from what has appeared in previous Indicators. The section, which was part of the unedited chapter on public attitudes toward science and technology, notes that 45% of Americans in 2008 answered true to the statement, "Human beings, as we know them today, developed from earlier species of animals." The figure is similar to previous years and much lower than in Japan (78%), Europe (70%), China (69%), and South Korea (64%). The same gap exists for the response to a second statement, "The universe began with a big explosion," with which only 33% of Americans agreed.

The sad thing is that one of the religious accommodationists responsible for arguing that knowledge of evolution and the big bang are "flawed indicators of scientific knowledge because responses conflated knowledge and beliefs," is an astrophysicist: Louis Lanzerotti, at the New Jersey Institute of Technology.

Lanzerotti isn't the only one to blame, as it seems a philosopher called John Bruer was the primary instigator of this pro-fundamentalist pandering.

When Science asked Bruer if individuals who did not accept evolution or the big bang to be true could be described as scientifically literate, he said: "There are many biologists and philosophers of science who are highly scientifically literate who question certain aspects of the theory of evolution," adding that such questioning has led to improved understanding of evolutionary theory. When asked if he expected those academics to answer "false" to the statement about humans having evolved from earlier species, Bruer said: "On that particular point, no."

If your arguments are trivially demolished within seconds of casual questioning by the Science reporter what business do you have being on the National Science Board?

[Bruer] calls the survey questions "very blunt instruments not designed to capture public understanding" of the two topics.

"I think that is a nonsensical response" that reflects "the religious right's point of view," says Jon Miller, a science literacy researcher at Michigan State University in East Lansing who authored the survey 3 decades ago and conducted it for NSF until 2001. "Evolution and the big bang are not a matter of opinion. If a person says that the earth really is at the center of the universe, even if scientists think it is not, how in the world would you call that person scientifically literate? Part of being literate is to both understand and accept scientific constructs."

Miller has it right. Lanzerotti and Bruer should be ashamed of themselves.

Interesting Astrophysics: Mar 23 to Mar 31

2010-04-02T09:10:00.002-04:00

Dwarfs and giants compete in this edition of Interesting Astrophysics. The dwarfs (or dwarves, as Tolkien would have us write it) are dwarf starburst galaxies and the giants are very very luminous starbursting galaxies.

There are two very nice papers on the very popular (if somewhat atypical) dwarf starburst galaxy NGC 1569 (Kepley et al, and Westmoquette et al), both of interest with respect to its galactic wind. Monreal-Ibero et al present a paper on NGC 5253 (possibly the second most popular dwarf starburst galaxy judged by number of papers published). And yes, that region of nitrogen enrichment that is the one clear case of localized chemical enrichment by recently formed massive stars is still there.

Younger et al discuss the physical sizes of the star forming regions in submillimeter galaxies, and argue that the data supports an interpretation as merger-driven starbursts rather than simply over-active disks. This is not particularly surprising, as the SMGs have long been thought to be semi-equivalent to local Ultraluminous IR galaxies (ULIRGs are merger driven starbursts).

Not content with merely Ultraluminosity, Rowan-Robinson et al present a catalog of 179 Hyperluminous IR galaxies, and discuss their spectral energy distributions and star formation rates.

Last but not least I'll mention Chen et al's work on probing outflows from star forming galaxies with Na I absorption in SDSS spectra. Its a big paper, but for me the results that seem coolest are that their results appear to confirm the Lehnert & Heckman star formation per unit area threshold above which winds (or extra-planar gas) appear, and that outflows really do seem to have a prefer opening angle of ~60 degrees.

Galaxies and Starbursts

The Role of the Magnetic Field in the Interstellar Medium of the Post-Starburst Dwarf Irregular Galaxy NGC 1569
Amanda A. Kepley, Stefanie Mühle, John Everett, Ellen G. Zweibel, Eric M. Wilcots and Uli Klein, 2010, ApJ, 712, 536

This is a really nice piece of work. Their are relatively few studies of magnetic field structures and strengths in starbursts with superwinds that answer the kind of questions that this paper addresses, so this paper is a very valuable addition to the literature.

Their abstract (emphasis mine): "NGC 1569 is a nearby dwarf irregular galaxy which underwent an intense burst of star formation 10-40 Myr ago. We present observations that reach surface brightnesses 2-80 times fainter than previous radio continuum observations and the first radio continuum polarization observations of this galaxy at 20 cm, 13 cm, 6 cm, and 3 cm. These observations allow us to probe the relationship of the magnetic field of NGC 1569 to the rest of its interstellar medium (ISM). We confirm the presence of an extended radio continuum halo at 20 cm and see for the first time the radio continuum feature associated with the western Hα arm at wavelengths shorter than 20 cm. Although, in general, the spectral indices derived for this galaxy steepen as one moves into the halo of the galaxy, there are filamentary regions of flat spectral indices extending to the edge of the galaxy. The spectral index trends in this galaxy support the theory that there is a convective wind at work in this galaxy. There is strong polarized emission at 3 cm and 6 cm and weak polarized emission at 20 cm and 13 cm. We estimate that the thermal fraction is 40%-50% in the center of the galaxy and falls off rapidly with height above the disk. Using this estimate, we derive a total magnetic field strength of 38 μG in the central regions and 10-15 μG in the halo. The magnetic field is largely random in the center of the galaxy; the uniform field is ~3-9 μG and is strongest in the halo. Using our total magnetic field strength estimates and the results of previous observations of NGC 1569, we find that the magnetic pressure is the same order of magnitude but, in general, a factor of a few less than the other components of the ISM in this galaxy. The uniform magnetic field in NGC 1569 is closely associated with the Hα bubbles and filaments. We suggest that a supernova-driven dynamo may be operating in this galaxy. Based on our pressure estimates and the morphology of the magnetic field, the outflow of hot gas from NGC 1569 is clearly shaping the magnetic field, but the magnetic field in turn may be aiding the outflow by channeling gas out of the disk of the galaxy. Dwarf galaxies with extended radio continuum halos like that of NGC 1569 may play an important role in magnetizing the intergalactic medium."

Mapping the roots of the galactic outflow in NGC1569
Mark S. Westmoquette, Linda J. Smith, Jay S. Gallagher and Katrina M. Exter, 2009, Ap&SS, 324, 187

The physical scale of the far-infrared emission in the most luminous submillimetre galaxies II: evidence for merger-driven star formation
J. D. Younger, G. G. Fazio, M. L. N. Ashby, F. Civano, M. Elvis, M. A. Gurwell, J.-S. Huang, D. Iono, A. B. Peck, G. R. Petitpas, K. S. Scott, D. J. Wilner, G. W. Wilson, M. S. Yun, arXiv:1003.4264 [pdf, ps, other]
Comments: 9 pages, 3 Figures, submitted to MNRAS

From their abstract: "These relatively compact sizes (<5-10 kpc) argue strongly for merger-driven starbursts, rather than extended gas-rich disks, as the preferred channel for forming SMGs. For the most luminous objects, the derived sizes may also have important physical consequences; under a series of simplifying assumptions, we find that these two objects in particular are forming stars close to or at the Eddington limit for a starburst."

Hyperluminous infrared galaxies from IIFSCz
Michael Rowan-Robinson, Lingyu Wang, arXiv:1003.4869 [pdf, ps, other]
Comments: 11 pages, 11 figures: accepted for publication in MNRAS.

From their abstract: "We present a catalogue of 179 hyperluminous infrared galaxies (HLIRGs) from the Imperial IRAS-FSS Redshift (IIFSCz) Catalogue. Of the 92 with detections in at least two far infrared bands, 62 are dominated by an M82-like starburst, 22 by an Arp220-like starburst and 8 by an AGN dust torus. On the basis of previous gravitational lensing studies and an examination of HST archive images for a further 5 objects, we estimate the fraction of HLIRGs that are significantly lensed to be 10-30%. ... The implied star-formation rates, even after correcting for lensing magnification, are in excess of 1000 Mo /yr."

A study of the interplay between ionized gas and star clusters in the central region of NGC 5253 with 2D spectroscopy
A. Monreal-Ibero, J. M. Vilchez, J. R. Walsh, C. Munoz-Tunon, arXiv:1003.5329 [pdf, ps, other]
Comments: accepted in Astronomy & Astrophysics. 21 pages, 22 figures

From their abstract: "A detailed 2D study of the central region of NGC5253 has been performed to characterize the stellar and ionized gas structure as well as the extinction distribution, physical properties and kinematics of the ionized gas in the central ~210pc x 130pc. ... The [SII]l6717/[SII]l6731 map shows an electron density (N_e) gradient declining from the peak of emission in Ha (790cm^-3) outwards, while the argon line ratio traces areas with $N_e~4200 - 6200cm^(-3). The area polluted with extra nitrogen, as deduced from the excess [NII]/Ha, extends up to distances of 3.3" (~60pc) from the maximum pollution, which is offset by ~1.5" from the peak of continuum emission. Wolf-Rayet features are distributed in an irregular pattern over a larger area (~100pc x 100pc) and associated with young stellar clusters. ... The line profiles are complex. Up to three emission components were needed to reproduce them. One of them, associated with the giant HII region, presents supersonic widths and [NII] and [SII] emission lines shifted up to 40km/s with respect to Ha. Similarly, one of the narrow components presents offsets in the [NII] line of <~20km/s. This is the first time that maps with such velocity offsets for a starburst galaxy have been presented."

Absorption-line probes of the prevalence and properties of outflows in present-day star-forming galaxies
Yan-Mei Chen, Christy A. Tremonti, Timothy M. Heckman, Guinevere Kauffmann, Benjamin J. Weiner, Jarle Brinchmann, Jing Wang, arXiv:1003.5425 [pdf, ps, other]
Comments: 18 pages, 18 figures, submitted to AJ

Their abstract: "We analyze star forming galaxies drawn from SDSS DR7 to show how the interstellar medium (ISM) Na I 5890, 5896 (Na D) absorption lines depend on galaxy physical properties, and to look for evidence of galactic winds. We combine the spectra of galaxies with similar geometry/physical parameters to create composite spectra with signal-to-noise ~300. The stellar continuum is modeled using stellar population synthesis models, and the continuum-normalized spectrum is fit with two Na I absorption components. We find that: (1) ISM Na D absorption lines with equivalent widths EW > 0.8A are only prevalent in disk galaxies with specific properties -- large extinction (Av), high star formation rates (SFR), high star formation rate per unit area ($\Sigma_{\rm SFR}$), or high stellar mass (M*). (2) the ISM Na D absorption lines can be separated into two components: a quiescent disk-like component at the galaxy systemic velocity and an outflow component; (3) the disk-like component is much stronger in the edge-on systems, and the outflow component covers a wide angle but is stronger within 60deg of the disk rotation axis; (4) the EW and covering factor of the disk component correlate strongly with dust attenuation, highlighting the importance that dust shielding may play the survival of Na I. (5) The EW of the outflow component depends primarily on $\Sigma_{\rm SFR}$ and secondarily on Av; (6) the outflow velocity varies from ~120 to 160km/s but shows little hint of a correlation with galaxy physical properties over the modest dynamic range that our sample probes (1.2 dex in log$\Sigma_{\rm SFR}$ and 1 dex in log M*)."

Massive star formation in Wolf-Rayet galaxies. III: Analysis of the O and WR populations
Angel R. Lopez-Sanchez, Cesar Esteban, arXiv:1004.0051 [pdf, ps, other]
Comments: Accepted in A&A, 19 pages, 13 figures

Black Holes and AGN

Infrared Excess Sources: Compton Thick QSOs, low luminosity Seyferts or starbursts?
A. Georgakakis, M. Rowan-Robinson, K. Nandra, J. Digby-North, P. G. Perez-Gonzalez, G. Barro, arXiv:1003.5218 [pdf, other]
Comments: Accepted by MNRAS

Full abstract: "We explore the nature of Infrared Excess sources (IRX), which are proposed as candidates for luminous L_X(2-10keV)>1e43erg/s Compton Thick (N_H>2e24cm^{-2}$) QSOs at z~2. Lower redshift, z~1, analogues of the distant IRX population are identified by firstly redshifting to z=2 the SEDs of all sources with secure spectroscopic redshifts in the AEGIS (6488) and the GOODS-North (1784) surveys and then selecting those that qualify as IRX sources at that redshift. A total of 19 galaxies are selected. The mean redshift of the sample is $z\approx1$. We do not find strong evidence for Compton Thick QSOs in the sample. For 9 sources with X-ray counterparts, the X-ray spectra are consistent with Compton Thin AGN. Only 3 of them show tentative evidence for Compton Thick obscuration. The SEDs of the X-ray undetected population are consistent with starburst activity. There is no evidence for a hot dust component at the mid-infrared associated with AGN heated dust. If the X-ray undetected sources host AGN, an upper limit of L_X(2-10keV) =1e43erg/s is estimated for their intrinsic luminosity. We propose that a large fraction of the $z\approx2$ IRX population are not Compton Thick QSOs but low luminosity [L_X(2-10keV)<1e43erg/s], possibly Compton Thin, AGN or dusty starbursts. It is shown that the decomposition of the AGN and starburst contribution to the mid-IR is essential for interpreting the nature of this population, as star-formation may dominate this wavelength regime. "

Numerical Methods and Hydrodynamics

A method for reconstructing the PDF of a 3D turbulent density field from 2D observations
Christopher M. Brunt, Christoph Federrath, Daniel J. Price, arXiv:1003.4151 [ps, pdf, other]
Comments: 5 pages, 2 figures, accepted for publication in MNRAS Letters

Theoretical Cosmology

Toward the Formation of Realistic Galaxy Disks
Alyson Brooks, arXiv:1003.3882 [pdf]
Comments: Proceedings of the Frank N. Bash Symposium 2009: "New Horizons in Astronomy." Comments welcome.

Stars, Supernovae and Planets

Direct Confirmation of the Asymmetry of the Cas A SN Explosion with Light Echoes
A. Rest, et al, arXiv:1003.5660 [pdf, ps, other]
Comments: 12 pages, 7 figures, submitted to ApJ

Spectral Classification; Old and Contemporary
Sunetra Giridhar, arXiv:1003.4002 [ps, pdf, other]
Comments: To be published in "Principles and Perspectives in Cosmochemistry" Lecture Notes on Kodai School on Synthesis of Elements in Stars: Ed Aruna Goswami & Eswar Reddy, Springer Verlag, 2009, 17 pages, 10 figures

Updating the Historical Sunspot Record
Leif Svalgaard, arXiv:1003.4666 [pdf, other]
Comments: SOHO23 Conference Proceedings, Astronomical Society of the Pacific

Abstract: "We review the evidence for the argument that Rudolf Wolf's calibration of the Sunspot Number is likely to be correct and that Max Waldmeier introduced an upwards jump in the sunspot number in 1945. The combined effect of these adjustments suggests that there has been no secular change in the sunspot number since coming out of the Maunder Minimum ~1700."

Interesting Astrophysics: Mar 08 to Mar 22

2010-03-22T11:21:00.002-04:00

I return from a much-needed holiday in the Caribbean to an energetic bunch of preprints and papers making its appearance in this edition of Interesting Astrophysics.

Galactic winds, including possible AGN-driven galactic winds, are of course my major interest, so Scannapieco & Brüggen's paper is of particular note, but note also Dadina et al, Shu et al (twice) and Jiménez-Vicente et al's papers.

X-ray emission from star forming galaxies also makes an appearance, with Wang's PNAS review, Owen & Warwick's XMM-Newton study of M33, and Anderson & Bregman's discussion of the baryon content of hot halos around galaxies. Martin Weisskopf's history of the project to build the Chandra X-ray Observatory is also well worth reading.

Galaxies and Starbursts

X-raying Galaxies: A Chandra Legacy
Q. Daniel Wang, arXiv:1003.1282 [pdf, other]
Comments: Refereed review article to be published in Proceedings of the National Academy of Sciences

The submillimetre properties of ultraluminous infrared galaxies
D. L. Clements, L. Dunne, S. Eales, 2010, MNRAS, 403, 274
Full Text: HTML, PDF (Size: 859K)

A blue tilt in the globular cluster system of the Milky Way-like galaxy NGC 5170
Duncan A. Forbes, Lee R. Spitler, W. E. Harris, Jeremy Bailin, Jay Strader, Jean P. Brodie, S. S. Larsen, 2010, MNRAS, 403, 429
Full Text: HTML, PDF (Size: 3707K)

The likeness of a galaxy to the Milky-Way often depends greatly on whose opinion you ask. NGC 5170 has a circular rotation velocity of ~250 km/s and a star formation rate of ~0.5 Solar masses per year, making it somewhat more massive and less active than the Milky Way. Nevertheless an interesting galaxy (No X-ray halo was detected around NGC 5170 in Chandra observations, see Pedersen et al 2006 and Rasmussen et al 2009. Note that the detection of an X-ray halo around NGC 5746 claimed in Pedersen et all 2006 was effectively retracted by Rasmussen et al 2009).

Ongoing Star Formation In AGN Host Galaxy Disks: A View From Core-collapse Supernovae
J. Wang, J. S. Deng, J. Y. Wei, arXiv:1003.1358 [ps, pdf, other]
Comments: 5 pages, 4 figures, accepted by MNRAS

A Region of Violent Star Formation in the Irr Galaxy IC 10: Structure and Kinematics of Ionized and Neutral Gas
O. V. Egorov, T. A. Lozinskaya, A. V. Moiseev, arXiv:1003.1705 [ps, pdf, other]
Comments: 22 pages, 10 figures; accepted in Astronomy Reports

Do Hot Haloes Around Galaxies Contain the Missing Baryons?
Michael E. Anderson, Joel N. Bregman, arXiv:1003.3273 [ps, pdf, other]
Comments: accepted for publication in the Astrophysical Journal

As with most papers that pose a question in their title, the answer is no. A nice paper worth looking at.

On The GeV & TeV Detections of the Starburst Galaxies M82 & NGC 253
Brian C. Lacki, Todd A. Thompson, Eliot Quataert, Abraham Loeb, Eli Waxman, arXiv:1003.3257 [ps, pdf, other]
Comments: 14 pages, emulateapj format, submitted to ApJ.

Black Holes and AGN

X-ray imaging of the ionisation cones in NGC 5252
M.Dadina, M.Guainazzi, M.Cappi, S.Bianchi, C. Vignali, G. Malaguti, A. Comastri, rXiv:1003.1665 [ps, pdf, other]
Comments: Accepted for publication in A&A

NGC 2992 in an X-ray high state observed by XMM: Response of the Relativistic Fe K$\alpha$ Line to the Continuum
X. W. Shu, T. Yaqoob, K. D. Murphy, V. Braito, J. X. Wang, W. Zheng, arXiv:1003.1789 [ps, pdf, other]
Comments: 30 pages, 6 figures, Accepted to ApJ

The Cores of the Fe Kα Lines in Active Galactic Nuclei: an Extended Chandra High Energy Grating Sample
X. W. Shu, T. Yaqoob, J. X. Wang, arXiv:1003.1790 [ps, pdf, other]
Comments: 54 pages, 7 figures, and 4 tables, to appear in ApJ Supplement Series

Blasts and shocks in the disc of NGC 4258
J. Jiménez-Vicente, E. Mediavilla, A. Castillo-Morales, E. Battaner, arXiv:1003.3635 [ps, pdf, other]
Comments: 7 pages, 10 colour figures. Accepted for publication in MNRAS.

Na I observations with an IFU.

Numerical Methods

General two-dimensional least-squares image subtraction
J. L. Quinn, A. Clocchiatti and M. Hamuy, 2010, MNRAS, 403, L1
Full Text: HTML, PDF (Size: 514K)

Shape: A 3D Modeling Tool for Astrophysics
Wolfgang Steffen, Nicholas Koning, Stephan Wenger, Christophe Morisset, Marcus Magnor, arXiv:1003.2012 [pdf, other]
Comments: 13 pages, 11 figures, accepted for publication in the "IEEE Transactions on Visualization and Computer Graphics"

Simulating Supersonic Turbulence in Galaxy Outflows
Evan Scannapieco, Marcus Brüggen, arXiv:1003.3234 [pdf, other]
Comments: 22 pages, 13 figures, MNRAS, in press

X-rays

Innovations in the Analysis of Chandra-ACIS Observations
Patrick S. Broos, Leisa K. Townsley, Eric D. Feigelson, Konstantin V. Getman, Franz E. Bauer, Gordon P. Garmire, arXiv:1003.2397 [pdf, other]
Comments: Accepted by the ApJ, 2010 Mar 10, 39 pages, 16 figures

The Making of the Chandra X-ray Observatory: the Project Scientist's Perspective
Martin C. Weisskopf, arXiv:1003.1990 [pdf]
Comments: 6 pages, 17 figures. To be published in the Proceedings of the national Academy of Sciences of the United States of America.

I found this to be a really interesting article. It discusses both technical and political development with a sprinkling of dry humor. Also note the time span between the conceptual birth of AXAF/Chandra (1963, and the updated 1976 proposal) and the actual launch in 1999.

Soft X-ray emission from the inner disc of M33
R. A. Owen and R. S. Warwick, 2010, MNRAS, 403, 558
Full Text: HTML, PDF (Size: 4702K)

Thanks, but I'm not worthy (Research Blogging Awards)

2010-03-08T09:19:00.004-05:00

Wow! Somehow this blog got into the finalist list for Research Blogging's best research blog of 2010.

I'm deeply flattered - thank you.

But seriously, my little part-time blog isn't anywhere near the quality of the other blogs on the nominee list.

I voted for Ed Yong's awesome Not Exactly Rocket Science, but if I'd had a second vote I'd also have voted for Eric Johnson's blog The Primate Diaries.

Interesting Astrophysics: 22 Feb to 05 Mar, 2010

2010-03-05T09:25:00.002-05:00

Of particular interest (to me at least) are a variety of papers related to galactic winds. The AKARI observations of Kaneda et al probe dust in M82's wind; Steidel et al use absorption lines probe the distribution and kinematics gas around redshift z~2-3 LBGs at impact parameters of - to ~100 kpc; Nestor et al propose to understand ultra-strong Mg II absorbers in the context of galactic winds; Alexander et al present evidence for a galactic wind in z~2 ULIRG; Sumui et al present a theoretical mixed Cosmic-ray/thermal wind model; and Pinsonneault et al consider the effects of galactic winds anisotropy in cosmological simulations.

In a similar vein, albeit not quite galactic winds, there is a conference proceedings by Proga et al on large scale outflows from AGN, and papers on dust in HII regions (Draine) and in wind-blown bubbles (Everett & Churchwell).

Quite of a few of these papers were noted in previous editions of "Interesting Astrophysics" when they appeared as preprints on arXiv.org, but its worth noting them again with their full journal reference information.

Galaxies and Starbursts

Large-scale distributions of mid- and far-infrared emission from the center to the halo of M82 revealed with AKARI
H. Kaneda, D. Ishihara, T.Suzuki, N. Ikeda, T. Onaka, M. Yamagishi, Y. Ohyama, T. Wada, A. Yasuda, arXiv:1002.4521 [pdf, ps, other]
Comments: 12 pages, 8 figures, accepted for publication in A&A

Full abstract: "The edge-on starburst galaxy M82 exhibits complicated distributions of gaseous materials in its halo, which include ionized superwinds driven by nuclear starbursts, neutral materials entrained by the superwinds, and large-scale neutral streamers probably caused by a past tidal interaction with M81. We investigate detailed distributions of dust grains and polycyclic aromatic hydrocarbons (PAHs) around M82 to understand their interplay with the gaseous components. We performed mid- (MIR) and far-infrared (FIR) observations of M82 with the Infrared Camera and Far-Infrared Surveyor on board AKARI. We obtain new MIR and FIR images of M82, which reveal both faint extended emission in the halo and very bright emission in the center with signal dynamic ranges as large as five and three orders of magnitude for the MIR and FIR, respectively. We detect MIR and FIR emission in the regions far away from the disk of the galaxy, reflecting the presence of dust and PAHs in the halo of M82. We find that the dust and PAHs are contained in both ionized and neutral gas components, implying that they have been expelled into the halo of M82 by both starbursts and galaxy interaction. In particular, we obtain a tight correlation between the PAH and H$\alpha$ emission, which provides evidence that the PAHs are well mixed in the ionized superwind gas and outflowing from the disk."

Discovery of an unusual new radio source in the star-forming galaxy M82: Faint supernova, supermassive blackhole, or an extra-galactic microquasar?
T. W. B. Muxlow, R. J. Beswick, S. T. Garrington, A. Pedlar, D. M. Fenech, M. K. Argo, J. van Eymeren, M. Ward, A. Zezas, A. Brunthaler, arXiv:1003.0994 [pdf, ps, other]
Comments: 6 pages, 3 figures (2 colour), MNRAS letters accepted

The Structure and Kinematics of the Circum-Galactic Medium from Far-UV Spectra of z~2-3 Galaxies
C. C. Steidel, D. K. Erb, A. E. Shapley, M. Pettini, N. A. Reddy, M. Bogosavljević, G. C. Rudie, O. Rakic, arXiv:1003.0679 [pdf, ps, other]
Comments: Submitted to ApJ, 22 February 2010. 32 pages, 24 figures

Full abstract: "We present new results on the kinematics and spatial distribution of metal-enriched gas within 125 kpc (physical) of Lyman Break galaxies at redshifts z~2-3. In particular, we demonstrate how rest-UV galaxy spectra can be used to obtain key spatial and spectral information more efficiently than possible with QSO sightlines. After recalibrating the measurement of galaxy systemic redshifts from their UV spectra, we investigate the kinematics of galaxy-scale outflows via the strong interstellar (IS) absorption and Lya emission lines (when present), as well as their dependence on other physical properties of the galaxies. We construct a sample of 512 close (1-15 arcsec) angular pairs of z~2-3 LBGs in which the spectra background galaxies probe the circumgalactic gas surrrounding those in the foreground. The close pairs, together with spectra of the foreground galaxies themselves, sample galactocentric impact parameters b=0-125 kpc (physical) at <z>=2.2. The ensemble provides a spatial map of cool gas as a function of galactocentric distance for a well-characterized population of galaxies. We propose a simple model that simultaneously matches the kinematics, depth, and profile shape of IS absorption and Lya emission lines, as well as the observed variation of absorption line strength (of HI, CII, CIV, SiII, SiIV) versus galactocentric impact parameter. We discuss the results of the observations in the context of "cold accretion", in which cool gas accretes via filamentary streams directly onto the central regions of galaxies. At present, we find little observational support for cool infalling material, whereas evidence supporting the large-scale effects of outflows is strong. Reconciling theory and observation on the subject of gas flows into and out of forming galaxies seems necessary."

The SAURON project – XVI. On the sources of ionization for the gas in elliptical and lenticular galaxies
Marc Sarzi, et al, 2010, MNRAS, 402, 2187
Full Text: HTML, PDF (Size: 15234K)

From their abstract: "Finally, in the most massive and slowly or non-rotating galaxies in our sample, which can retain a massive X-ray halo, the finding of a spatial correlation between the hot and warm phases of the interstellar medium (ISM) suggests that the interaction with the hot ISM provides an additional source of ionization besides old ultraviolet-bright stars."

Note that they consider the X-ray gas static, as opposed to the SN Ia-driven wind scenario favored by Wang. Of course the kinematics of the WIM should provide insight into whether there is a bulk flow or not...

AINUR: Atlas of Images of NUclear Rings
S. Comerón, J. H. Knapen, J. E. Beckman, E. Laurikainen, H. Salo, I. Martínez-Valpuesta and R. J. Buta, 2010, MNRAS, 402, 2462
Full Text: HTML, PDF (Size: 10365K)

Cosmic ray driven outflows from high-redshift galaxies
Saumyadip Samui, Kandaswamy Subramanian and Raghunathan Srianand, 2010, MNRAS, 402, 2778
Full Text: HTML, PDF (Size: 1035K)

Searching for evidence of energetic feedback in distant galaxies: a galaxy wide outflow in a z ≈ 2 ultraluminous infrared galaxy
D. M. Alexander, A. M. Swinbank, Ian Smail, R. McDermid and N. P. H. Nesvadba, MNRAS, 402, 2211
Full Text: HTML, PDF (Size: 1066K)

Anisotropic Galactic Outflows and Enrichment of the Intergalactic Medium. II. Numerical Simulations

Steeve Pinsonneault, Hugo Martel, Matthew M. Pieri, arXiv:1002.4881 [pdf, ps, other]

Comments: Submitted to ApJ. Figures 4, 5 and 6 are not included because of their large sizes. They can be downloaded from: this http URL

Large scale outflows from z ~ 0.7 starburst galaxies identified via ultra-strong MgII quasar absorption lines
Daniel B. Nestor, Benjamin D. Johnson, Vivienne Wild, Brice Ménard, David A. Turnshek, Sandhya Rao, Max Pettini, arXiv:1003.0693 [pdf, ps, other]
Comments: 14 pages, 6 figure, to be submitted to MNRAS

Their abstract: "(Abridged) Star formation-driven outflows are a critically important phenomenon in theoretical treatments of galaxy evolution, despite our limited ability to trace them across cosmological timescales. It has been suggested that the strongest QAL systems might arise in such outflows. If confirmed, "Ultra-strong" MgII (USMgII) absorbers may identify galactic winds over a huge baseline in cosmic time, independently of the luminous properties of the galaxy. To this end, we present the first detailed imaging/spectroscopic study of the fields of two USMgII absorber systems culled from a statistical absorber catalog, to investigate the physical processes leading to the large velocity spreads that define such systems. Each field contains two bright emission-line galaxies at similar redshift to that of the absorption. Their specific SFRs are among the highest for their masses at these redshifts, and their 4000A break and Balmer absorption strengths imply they have undergone recent (~ 0.01-1 Gyr) starbursts. The concomitant presence of two rare phenomena - starbursts and USMgII absorbers - strongly implies a causal connection. We consider these data and USMgII absorbers in general in the context of various models, and conclude that galactic outflows are generally necessary to account for the velocity-extent of the absorption, favouring starburst driven outflows over tidally-stripped gas from a major interaction which triggered the starburst. Unlike past discoveries of blueshifted gas in the spectra of galaxies at cosmological distances, identifying outflows in this manner unambiguously demonstrates that the material reaches the IGM. Finally, we discuss the implications of these results and speculate on the overall contribution of such systems to the global SFR density at z ~ 0.7."

Black Holes and AGN

Large-Scale Outflows from AGN: a link between central black holes and galaxies
Daniel Proga, Ryuichi Kurosawa, Kentaro Nagamine, arXiv:1002.4896 [pdf, ps, other]
Comments: 8 pages, 2 figures. To be published in the Proceedings of IAU Symposium 267 "Co-Evolution of Central Black Holes and Galaxies"

Cosmology

A sub-resolution multiphase interstellar medium model of star formation and SNe energy feedback
Giuseppe Murante, Pierluigi Monaco, Martina Giovalli, Stefano Borgani, Antonaldo Diaferio, arXiv:1002.4122 [pdf, ps, other]
Comments: 23 pages, 26 figures, MNRAS accepted

Note to self: I need to have a careful look at what they assume about the energy efficiency of SN feedback.

Interstellar Medium and Hydrodynamics

On Radiation Pressure in Static, Dusty HII Regions

B. T. Draine, arXiv:1003.0474 [pdf, ps, other]

Comments: submitted to ApJ

Dusty Wind-Blown Bubbles
John E. Everett, Ed Churchwell, arXiv:1003.0838 [pdf, ps, other]
Comments: 13 pages, 14 figures, Accepted to ApJ

rpSPH: a much improved Smoothed Particle Hydrodynamics Algorithm
Tom Abel, arXiv:1003.0937 [pdf, other]
Comments: 14 pages, 11 figures, submitted to MNRAS. Comments welcome

Let the flame wars among the SPH community commence!

Stars, Supernovae and Planets

Bacterial survival in Martian conditions
Giuseppe Galletta; Giulio Bertoloni; Maurizio D'Alessandro, arXiv:1002.4077 [pdf, ps, other]
Comments: 5 pages, 3 figures, special issue of Planetary and Space science on Methane on Mars discovery. Topics: Astrobiology - Methods: laboratory - Mars - Panspermia

Full abstract: "We shortly discuss the observable consequences of the two hypotheses about the origin of life on Earth and Mars: the Lithopanspermia (Mars to Earth or viceversa) and the origin from a unique progenitor, that for Earth is called LUCA (the LUCA hypothesis). To test the possibility that some lifeforms similar to the terrestrial ones may survive on Mars, we designed and built two simulators of Martian environments where to perform experiments with different bacterial strains: LISA and mini-LISA. Our LISA environmental chambers can reproduce the conditions of many Martian locations near the surface trough changes of temperature, pressure, UV fluence and atmospheric composition. Both simulators are open to collaboration with other laboratories interested in performing experiments on many kind of samples (biological, minerals, electronic) in situations similar to that of the red planet. Inside LISA we have studied the survival of several bacterial strains and endospores. We verified that the UV light is the major responsible of cell death. Neither the low temperature, nor the pressure, nor the desiccation or the atmospheric changes were effective in this sense. We found that some Bacillus strains have a particular capability to survive for some hours in Martian conditions without being screened by dust or other shields. We also simulated the coverage happening on a planet by dust transported by the winds, blowing on the samples a very small quantity of volcanic ash grains or red iron oxide particles. Samples covered by these dust grains have shown a high percentage of survival, indicating that under the surface dust, if life were to be present on Mars in the past, some bacteria colonies or cells could still be present."

SciAm asks "Does the U.S. Produce Too Many Scientists?"

2010-02-22T15:12:00.002-05:00

Does the U.S. Produce Too Many Scientists?

American science education lags behind that of many other nations, right? So why does it produce so many talented young researchers who cannot find a job in their chosen field of study?

Headline of a lengthy online article at Scientific American.

I've reproduced my comment (slightly edited to fix some minor grammatical errors) below:

A poor title for the article. A better one would be "Are there enough scientific careers for scientists in the US?"

Within astrophysics there certainly is a massive demographic imbalance between the number of talented and committed PhD students continuing in academia as postdocs and soft-money researchers, and the number of tenured and tenure-equivalent jobs. Everyone knows this, at least when they're doing the PhD. They just make the mistake of thinking that if they're talented and love research that they'll get the job they're qualified for.

The problem is not that there is a career pyramid with significant losses of personal at each level compared to the old days of a few postdoc positions that fed directly into a similar number of tenured positions.

The problems are that (a) progression or success is more lottery than meritocracy (for a number of annoying reasons, but shear numbers of job candidates is one), and (b) there is no real career track for those who aren't lucky enough to land a classic tenure-track job.

University administrations and tenured faculty have little inclination to change this: the postdocs do much of the research, and are expendable as they're easily replaceable (by similarly talented and eager applicants). Soft money scientists bring in large amounts of overhead to the Universities, and even if many leave when their patience or grants run out their ranks are always easily filled by former postdocs desperate to carry on doing what they love.

And that "dskan" commenter - what alternate Universe did they come from?

Interesting Astrophysics: Feb 01 to Feb 19, 2010

2010-02-19T10:39:00.002-05:00

I have no time to provide commentary, so without further interruption here are the papers and preprints that I consider interesting that have appeared over the period Feb 01-19, 2010.

Galaxies and Starbursts

The AGN properties of the starburst galaxy NGC 7582
T.V. Ricci, J.E. Steiner, R.B. Menezes, A. Garcia-Rissmann, R. Cid Fernandes, arXiv:1001.5269 [ps, pdf, other]
Comments: 1 page, 2 figures, to be published in the Proceedings of the IAU Symposium no. 267

The stellar populations of the AGN/Starburst galaxy NGC7582
T.V. Ricci, J.E. Steiner, R.B. Menezes, A. Garcia-Rissmann, R. Cid Fernandes, arXiv:1001.5271 [ps, pdf, other]
Comments: 2 pages, 2 figures, to be published in the Proceedings of the IAU Symposium no. 262

Their abstract: "NGC 7582 is defined as a Starburst/AGN galaxy, since its optical and X-Ray spectra reveal both characteristics. In this work, we show the results of a stellar population modeling in a datacube taken with the Gemini South telescope. We found that $\sim$ 90% of the light in the field of view is emitted by stars that are less than 1 billion years old. A strong burst occurred about $\sim$ 6 million years ago and has nearly solar metallicity. We also found a Wolf-Rayet cluster."

Star Formation in the Outer Filaments of NGC 1275
R.E.A. Canning, A.C. Fabian, R.M. Johnstone, J.S. Sanders, C.J. Conselice, C.S. Crawford, J.S. Gallagher III, E. Zweibel, arXiv:1002.1056 [pdf, ps, other]
Comments: Accepted for publication in MNRAS, 14 pages, 14 figures, 3 tables

A panoramic view of the Milky Way analogue NGC 891
M. Mouhcine, R. Ibata, M. Rejkuba, arXiv:1002.0461 [pdf, ps, other]
Comments: 2 figures, Apj Letter, in press

A panoramic view of M81: New stellar systems in the debris field
M. Mouhcine, R. Ibata, arXiv:1002.0456 [pdf, ps, other]
Comments: 8 pages, MNRAS

Evidence of Early Enrichment of the Galactic Disk by Large-Scale Winds
T. Tsujimoto, J. Bland-Hawthorn, K.C. Freeman, arXiv:1002.3181 [pdf, ps, other]
Comments: 9 pages including 5 figures, accepted for publication in PASJ

Starburst evolution: free-free absorption in the radio spectra of luminous IRAS galaxies
M. S. Clemens, A. Scaife, O. Vega, A. Bressan, arXiv:1002.3334 [pdf, ps, other]
Comments: 13 pages, 5 figures, accepted by MNRAS

Metal-line emission from the warm-hot intergalactic medium: II. Ultraviolet
Serena Bertone, Joop Schaye, C.M. Booth, Claudio Dalla Vecchia, Tom Theuns, Robert P.C. Wiersma, arXiv:1002.3393 [pdf, ps, other]
Comments: 21 pages, 22 figures. Submitted to MNRAS

Their abstract: "Approximately half the baryons in the local Universe are thought to reside in the warm-hot intergalactic medium (WHIM). Emission lines from metals in the UV band are excellent tracers of the cooler fraction of this gas. We present predictions for the surface brightness of a sample of UV lines that could potentially be observed by the next generation of UV telescopes at z<1. We use a subset of simulations from the OWLS project to create emission maps and to investigate the effect of varying the physical prescriptions for star formation, supernova and AGN feedback, chemodynamics and radiative cooling. Most models produce results in agreement within a factor of a few, indicating that the predictions are robust. Of the lines we consider, C III is the strongest line, but it typically traces gas colder than 10^5 K. The same is true for Si IV. The second strongest line, C IV, traces circum-galactic gas with T~10^5 K. O VI and Ne VIII probe the warmer (T~10^5.5 K and T~10^6 K, respectively) and more diffuse gas that may be a better tracer of the large scale structure. N V emission is intermediate between C IV and O VI. The intensity of all emission lines increases strongly with gas density and metallicity, and for the bright emission it is tightly correlated with the temperature for which the line emissivity is highest. In particular, the C III, C IV, Si IV and O VI emission that is sufficiently bright to be potentially detectable in the near future (>10^3 photon/s/cm^2/sr), comes from relatively dense (rho>10^2 rho_mean) and metal rich (Z>0.1 Z_sun) gas. As such, emission lines are highly biased tracers of the missing baryons and are not an optimal tool to close the baryon budget. However, they do provide a powerful means to detect the gas cooling onto or flowing out of galaxies and groups. (Abridged)"

Black Holes and AGN

Timing the starburst-AGN connection
Vivienne Wild, Timothy Heckman, Stephane Charlot, arXiv:1002.3156 [pdf, ps, other]
Comments: 16 pages, 12 figures, accepted for publication in MNRAS

Interstellar Medium

Metal-Ion Absorption in Conductively Evaporating Clouds
Orly Gnat, Amiel Sternberg, Christopher F. McKee, arXiv:1002.1309 [pdf, ps, other]
Comments: Submitted to ApJ

ITERA: IDL Tool for Emission-line Ratio Analysis
Brent Groves, Mark Allen, arXiv:1002.3372 [pdf, ps, other]

Comments: Accepted for New Astronomy, 3 figures. ITERA tool available to download from this http URL

Stars, Supernove and Planets

The Birth Environment of the Solar System
Fred C. Adams, arXiv:1001.5444 [ps, pdf, other]
Comments: 58 pages including 7 figures, to appear in Annual Reviews of Astronomy and Astrophysics (2010, Vol. 48)

Absract in full: "This paper reviews our current understanding of the possible birth environments of our Solar System. Since most stars form within groups and clusters, the question becomes one of determining the nature of the birth aggregate of the Sun. This discussion starts by reviewing Solar System properties that provide constraints on our environmental history. We then outline the range of star-forming environments that are available in the Galaxy, and discuss how they affect star and planet formation. The nature of the solar birth cluster is constrained by many physical considerations, including radiation fields provided by the background environment, dynamical scattering interactions, and by the necessity of producing the short-lived radioactive nuclear species inferred from meteoritic measurements. Working scenarios for the solar birth aggregate can be constructed, as discussed herein, although significant uncertainties remain."

A scenario of planet erosion by coronal radiation
J. Sanz-Forcada, I. Ribas, G. Micela, A. M. T. Pollock, D. Garcia-Alvarez, E. Solano, C. Eiroa, arXiv:1002.1875 [pdf, ps, other]
Comments: Accepted by A&A Letters (8 Feb. 2010). 4 pages, 3 figures, 1 online table (included)

On the Disruption of Star Clusters in a Hierarchical Interstellar Medium
Bruce G. Elmegreen, Deidre A. Hunter, arXiv:1002.2823 [pdf, ps, other]
Comments: ApJ vol. 712, March 20, 2010, 33 pages 15 figures

Do Wolf-Rayet stars have similar locations in hosts as type Ib/c supernovae and long gamma-ray bursts?
G. Leloudas, J. Sollerman, A. J. Levan, J. P. U. Fynbo, D. Malesani, J. R. Maund, arXiv:1002.3164 [pdf, ps, other]
Comments: Under review in A&A. The present version includes suggestions from the referee

Online latex equation editor with gif/png output

2010-02-17T20:36:00.003-05:00

Very useful for talks: http://www.codecogs.com/components/equationeditor/equationeditor.php

E.g.

You can't trust grades, and can't trust letters of recommendation, so what can you trust?

2010-02-01T17:52:00.005-05:00

There is an hidden disadvantage for students here. A-B-C-D-F grades have become nearly useless as entry gauges for many professions (the article emphasizes nursing and education). That means that employers have to lean more and more on other indicators. Letters of recommendation are more inflated than grades, so they don't help. That brings us to tangible things like internships, standardized test scores, and interviews.

Oh and intangibles. Like nepotism.

From John Hawk's paleoanthropology weblog, discussing grade inflation.

Personally this paragraph hits home for two reasons:

Having both written and read Astronomy job-related letters of recommendation I certainly think there is a huge variance in their accuracy and honesty, yet they seem to be given greater weight than objective publication records and citation counts. Possibly a majority are semi-accurate, but there is a sizable minority that are hyped out of all resemblance to reality (some I have read you might are laughable or must be jokes, except the joke is on the rest of us when those candidates get the nice jobs). The sad fact of the matter is that given that the number of higher level astro jobs available is always smaller than the number of qualified applicants such inflated letters of recommendation do often appear to work... at least in the cases where I have read seemingly hyped letters of recommendation for a candidate, and later investigate their papers and follow their career progression.
Having just had to look into what my high school grades were for the first time in almost twenty years I was very annoyed to also find that GCSE's and A-levels (this was the UK) have suffered monotonic grade inflation for approximately the last 30 years. What were pretty damn good grades for the time now seem average. And its not just that schools are better at teaching to slowly varying exams (or that students are smarter - hah!)... they're now giving out C grades in GCSE science if get only 18% of the questions right and A* grades if you get 51%.

[GPA grade inflation graph from Harold Marcuse (UC Santa Barbara)]

Geoffrey Burbidge passes away (Jan 26 2010)

2010-01-30T21:40:00.009-05:00

UCSD reports that Geoffrey Burbidge passed away on January 26th, 2010, after a long illness.

I extend my condolences to his surviving family and friends.

He will be remembered for seminal contributions to astrophysics, in particular our understanding of stellar nucleosynthesis and chemical evolution (Burbidge, Burbidge, Fowler & Hoyle, 1957, Rev. Mod. Phys. 29, 547), his long stint as editor of Annual Reviews of Astronomy & Astrophysics, and his quixotic refusal to accept a Big Bang cosmology even in the face of overwhelming evidence for it and against Hoyle's and his favored Steady State models.

I must admit I have much tolerance for the Burbidge's peculiarities than for Hoyle (e.g. the crazy anti-evolution stuff).

That the Burbidges did some of the early work on M82's wind (Burbidge, Burbidge & Rubin, 1964, AJ, 69, 535; Burbidge, Burbidge & Rubin, 1964, ApJ, 140, 942; although admittedly they thought it a non-thermal phenomenon possibly related to the contemporarily discovered quasar/QSO phenomenon, and also Lynds & Sandage's paper on M82 came before theirs) certainly helps.

More recently (various papers between 1980 to 2003) the Burbidge's interest in M82 has been with identifying QSOs that are nearby to M82. Of course they believed there were unusual areal densities of QSOs near galaxies like M82, which they thought meant that QSOs were ejected from the centers of galaxies (Steady State cosmologies required continual creation of matter ex-nihilo) and that the QSO's much higher redshifts were non-cosmological. But papers, including those papers, can still be scientifically useful even you don't have to believe the author's interpretations. QSOs can be used as background light sources to probe the intergalactic medium around galaxies, and with a sufficiently sensitive detector this can be used to probe the extent of the IGM around M82 and the extent of its wind - this could answer important unanswered questions about the galactic winds. Sadly the QSOs near M82 are too faint for this technique to be currently useful... but at some point in the future those QSO will be good targets. But you need to have a list of the coordinates and brightness of your candidate background QSOs, and the Burbidge's (and Arp) have spent a lot of telescope time finding QSOs in the sky near galaxies when few other astronomers were interested in doing so.

[The image of Geoffrey Burbidge shown here, credit UCSD, is dated 1966.]

Interesting Astrophysics: Jan 18 to Jan 29

2010-01-29T09:25:00.003-05:00

Of particular note among the crop of preprint and papers released within the last two week are observational and theoretical papers on galactic winds (Sharp & Hawthorn; Choi & Nagamine), and the physics of dust-driven flows (Miniati; Ivezic & Elitzur). Other papers cover feedback ad galaxy scaling relations (Dutton & van den Bosch; Spitoni et al), universality versus variations in the IMF (Bastian et al) and a slew of planet related papers.

Galaxies and Starbursts

The Impact of Feedback on Disk Galaxy Scaling Relations
Aaron A. Dutton, Frank C. van den Bosch, arXiv:1001.3406 [ps, pdf, other]
Comments: 7 pages, 2 figures. To appear in proceedings of "Galaxy Evolution: Emerging Insights and Future Challenges", November 11-14, 2008, The University of Texas at Austin
Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

Their abstract: "We use a disk formation model to study the effects of galactic outflows (a.k.a. feedback) on the rotation velocity - stellar mass - disk size, gas fraction - stellar mass, and gas phase metalicity - stellar mass scaling relations of disk galaxies. We show that models without outflows are unable to explain these scaling relations, having both the wrong slopes and normalization. The problem can be traced to the model galaxies having too many baryons. Models with outflows can solve this "over-cooling" problem by removing gas before it has time to turn into stars. Models with both momentum and energy driven winds can reproduce the observed scaling relations. However, these models predict different slopes which, with better observations, may be used to discriminate between these models."

Pet peeve. Galactic winds are not either exclusively momentum-driven or energy-driven. The standard model of starburst-driven winds is a multi-phase wind model, and some phases are best described as energy driven and some phases better as momentum driven.

Gas circulation and galaxy evolution
Filippo Fraternali, arXiv:1001.3879 [ps, pdf, other]
Comments: 12 pages, 5 figures. Invited review at the conference "Hunting for the Dark: The Hidden Side of Galaxy Formation", Malta, 19-23 Oct. 2009. Eds. V.P. Debattista and C.C. Popescu, AIP Conf. Ser

3D Integral Field Observations of Ten Galactic Winds - I. Extended phase (>10 Myr) of mass/energy injection before the wind blows
R.G. Sharp, J. Bland-Hawthorn, arXiv:1001.4315 [pdf, other]

Comments: 43 pages, 30 figures, Accepted for publication in ApJ Jan-2010, Full resolution figures available from: this http URL

Haven't read, but abstract sounds provocative.

The issue of whether the apparent differences between outflows from different starburst galaxies is evolutionary (i.e. they change with time, and different galaxies are observed at different times) or environmental (winds in dwarf starbursts may have different intrinsic structure or visibility in comparison to a wind from a massive spiral or Ultraluminous IR galaxy, and that winds may not change much in *observable* properties as they age) is an old question, and I doubt it will go away soon.

The Origin of the Mass-Metallicity relation: an analytical approach
E. Spitoni, F. Calura, F. Matteucci, S. Recchi, rXiv:1001.4374 [ps, pdf, other]
Comments: Accepted by A&A

From their abstract: "The existence of a mass-metallicity (MZ) relation in star forming galaxies at all redshift has been recently established. We aim at studying some possible physical mechanisms contributing to the MZ relation by adopting analytical solutions of chemical evolution models including infall and outflow. ... It is difficult to disentangle among the outflow and IMF solutions only by considering the MZ relation, and other observational constraints should be taken into account to select a specific solution. For example, a variable efficiency of star formation increasing with galactic mass can also reproduce the MZ relation and explain the downsizing in star formation suggested for ellipticals. The best solution could be a variable efficiency of star formation coupled with galactic winds, which are indeed observed in low mass galaxies."

Black Holes and AGN

AGN population in Hickson's Compact Groups. I. Data and Nuclear Activity Classification
M.A. Martinez, A. del Olmo, R. Coziol, J. Perea, arXiv:1001.2825 [ps, pdf, other]
Comments: 44 pages, 8 figures and 5 tables. Accepted for publication in AJ

Spectral Energy Distributions of Weak Active Galactic Nuclei Associated With Low-Ionization Nuclear Emission Regions
Michael Eracleous, Jason A. Hwang, Helene M. L. G. Flohic, arXiv:1001.2924 [ps, pdf, other]
Comments:
emulateapj format, 12 pages in total, to appear in ApJS, one large table and one large figure abridged (will be available in electronic journal)

Cosmology and the IGM

Confirmation of X-Ray Absorption by WHIM in the Sculptor Wall
Taotao Fang, David A. Buote, Philip J. Humphrey, Claude R. Canizares, Luca Zappacosta, Roberto Maiolino, Gianpiero Tagliaferri, Fabio Gastaldello, arXiv:1001.3692 [ps, pdf, other]
Comments: 11 pages, 5 figures. Submitted to ApJ

Hydrodynamics and Numerical Astrophysics

High-Order Finite Difference GLM-MHD Schemes for Cell-Centered MHD
A. Mignone, P. Tzeferacos, G. Bodo, arXiv:1001.2832 [ps, pdf, other]
Comments: 32 pages, 14 figure, submitted to Journal of Computational Physics (Aug 7 2009)

Note to self: Read this.

Multiphase and Variable Velocity Galactic Outflow in Cosmological SPH Simulations
Jun-Hwan Choi, Kentaro Nagamine, arXiv:1001.3525 [ps, pdf, other]

Comments: 13 pages, 10 figures, and 1 table submitted to MNRAS. A full resolution version is available at this http URL

Their abstact: "We develop a new multiphase and variable velocity (MVV) galactic outflow model for cosmological smoothed particle hydrodynamic (SPH) simulations. The MVV wind model captures the multiphase nature of the outflow, and the mass-loading factor in the MVV model is a function of galaxy stellar mass. We find that the simulation with the MVV outflow has the following characteristics: (i) the intergalactic medium (IGM) is hardly heated up, and the mean IGM temperature is almost the same as in the no-wind run; (ii) it has lower cosmic star formation rates (SFRs) compared to the no-wind run, but higher SFRs than the constant velocity wind run; (iii) it roughly agrees with the observed IGM metallicity, and roughly follows the observed evolution of Omega(Civ); (iv) the lower mass galaxies have larger mass-loading factors, and the low-mass end of galaxy stellar mass function is flatter than in the previous simulations. Therefore the MVV outflow model mildly alleviates the problem of too steep galaxy stellar mass function seen in the previous SPH simulations. In summary, the new MVV outflow model shows reasonable agreement with observations, and gives better results than the constant velocity wind model."

Will need to read this to see what exactly they've implemented and how it differs from the Oppenheimer/Davé mass-loaded wind model.

A Hybrid Scheme for Gas-Dust Systems Stiffly Coupled via Viscous Drag
Francesco Miniati, arXiv:1001.4794 [ps, pdf, other]
Comments: 41 pages, 3 figures, 14 tables, accepted to J. Comp. Phys.

Supernova-driven Turbulence and Magnetic Field Amplification in Disk Galaxies
Oliver Gressel, arXiv:1001.5187 [pdf, other]
Comments: 99 pages, 46 figures (in part
strongly degraded), 8 tables, PhD thesis, University of Potsdam (2009).
Resolve URN "urn:nbn:de:kobv:517-opus-29094" (e.g. via this http URL) for a version with high-resolution figures

High Energy Astrophysics

The International X-ray Observatory
Nicholas E. White, Arvind Parmar, Hideyo Kunieda, Kirpal Nandra, Takaya Ohashi, Jay Bookbinder, arXiv:1001.2843 [pdf, other]
Comments: 6 pages, 3 figures, for conference "X-ray Astronomy 2009 Present status, multi-wavelength approach and future perspectives"

I'm still very pleased with the IXO versus Chandra figure I made for the IXO folks last year (LHS panel in Fig 2).

Stars, Supernovae, and Planets

The Interior Dynamics of Water Planets
Roger Fu, Richard J. OConnell, Dimitar D. Sasselov, arXiv:1001.2890 [pdf, other]
Comments: 9 page 4 figures
Journal-ref: ApJ 708:1326 1334, 2010 January 10

The Diversity of Extrasolar Terrestrial Planets
J. C. Bond, D. S. Lauretta, D. P. O'Brien, arXiv:1001.3901 [ps, pdf, other]
Comments: 4 pages, 1 figure. Submitted to the proceedings of IAU symposium 265 Chemical Abundances in the Universe: Connecting First Stars to Planets

From their abstract: "A wide variety of resulting planetary compositions exist, ranging from those that are essentially "Earth-like", containing metallic Fe and Mg-silicates, to those that are dominated by graphite and SiC. This implies that a diverse range of terrestrial planets are likely to exist within extrasolar planetary systems."

Rocky Planetesimals as the Origin of Metals in DZ Stars
J. Farihi, M.A. Barstow, S. Redfield, P. Dufour, N.C. Hambly, arXiv:1001.5025 [ps, pdf, other]
Comments: Accepted to MNRAS

A Universal Stellar Initial Mass Function? A Critical Look at Variations
Nate Bastian, Kevin R. Covey, Michael R. Meyer, arXiv:1001.2965 [ps, pdf, other]
Comments: 49 pages, 5 figures, to appear in Annual Reviews of Astronomy and Astrophysics (2010, volume 48)

Full abstract: "Few topics in astronomy initiate such vigorous discussion as whether or not the initial mass function (IMF) of stars is universal, or instead sensitive to the initial conditions of star formation. The distinction is of critical importance: the IMF influences most of the observable properties of stellar populations and galaxies, and detecting variations in the IMF could provide deep insights into the process by which stars form. In this review, we take a critical look at the case for IMF variations, with a view towards whether other explanations are sufficient given the evidence. Studies of the field, local young clusters and associations, and old globular clusters suggest that the vast majority were drawn from a "universal" IMF: a power-law of Salpeter index ($\Gamma=1.35$) above a few solar masses, and a log normal or shallower power-law ($\Gamma \sim 0-0.25$) between a few tenths and a few solar masses (ignoring the effects of unresolved binaries). The shape and universality of the IMF at the stellar-substellar boundary is still under investigation and uncertainties remain large, but most observations are consistent with a IMF that declines ($\Gamma < -0.5$) well below the hydrogen burning limit. Observations of resolved stellar populations and the integrated properties of most galaxies are also consistent with a "universal IMF", suggesting no gross variations in the IMF over much of cosmic time. There are indications of "non-standard" IMFs in specific local and extragalactic environments, which clearly warrant further study. Nonetheless, there is no clear evidence that the IMF varies strongly and systematically as a function of initial conditions after the first few generations of stars."

Dusty winds II. Observational Implications
Zeljko Ivezic, Moshe Elitzur, arXiv:1001.4579 [ps, pdf, other]
Comments: 11 pages, 12 figures

Compares models and observations of dust-driven AGB winds.

Hard diffuse X-ray emission in the star-forming region ON2: discovery with XMM-Newton
L.M. Oskinova, R.A. Gruendl, R. Ignace, W.-R. Hamann, Y.-H. Chu, A. Feldmeier, arXiv:1001.4798 [ps, pdf, other]

Comments: ApJ, in press. Reduced fig. resolution. Full resolution version is at this http URL

From their abstract: "We obtained X-ray XMM-Newton observations of the open cluster Berkely 87 and the massive star-forming region (SFR) ON 2. ... The two patches of diffuse X-ray emission are encompassed in the shell-like H II region GAL 75.84+0.40 in the northern part of ON 2 and in the ON 2S region in the southern part of ON 2. ... Its spectrum can be fitted either with a thermal plasma model at T < 30 MK or by an absorbed power-law model with gamma; approx. -2.6. The X-ray luminosity of GAL 75.84+0.40 is L_X approx. 1 10^32 erg/s. The diffuse emission from ON 2S is adjacent to the ultra-compact H II (UCHII) region Cygnus 2N, but does not coincide with it or with any other known UCHII region. It has a luminosity of L_X approx. 6 10^31 erg/s. The spectrum can be fitted with an absorbed power-law model with gamma; approx.-1.4. ... We suggest that SFR ON 2 emits hard diffuse X-rays by a synchrotron mechanism, invoked by the co-existence of strongly shocked stellar winds and turbulent magnetic fields in the star-forming complex."

Soft money

2010-01-21T22:39:00.003-05:00

I'm looking forward to seeing what the NAS Astro2010 Decadal Survey's "state of the profession" has to say regarding soft money and career tracks in Astronomy, but I see via DrugMonkey that the Director of the NIH (yes, that Francis Collins) is muttering about soft money, Universities and career tracks in the Chronicle of Higher Education (subscription only).

Interesting Astrophysics: 01 Jan to 15 Jan, 2010

2010-01-15T11:17:00.002-05:00

The first two weeks of 2010 have produced a number of interesting papers and preprints.

Of particular interest to me are starburst/galactic wind related papers (Moiseev et al; Westmoquette et al; Beaulieu et al), hot gas in galaxy halos (Nipoti; Marinacci et al), and AGN outflows (Morganti et al; Storchi-Bergmann).

Finally, the International X-ray Observatory team's response to the NAS's Astro2010 Decadal Survey's Request For Information (Bookbinder et al) is well worth a read, particularly if you're not familiar with X-ray astronomy's unique capabilities.

Galaxies and Starbursts

Ionized gas outflow in the isolated S0 galaxy NGC 4460
Authors: Alexei Moiseev, Igor Karachentsev, Serafim Kaisin, arXiv:1001.0234 [ps, pdf, other]
Comments: 11 pages, 7 figures; accepted by MNRAS

From their abstract: "We use integral-field and long-slit spectroscopy to study the bright extended nebulosity discovered in the isolated lenticular galaxy NGC 4460 during a recent H-alpha survey of nearby galaxies. An analysis of archival SDSS, GALEX, and HST images indicates that current star formation is entirely concentrated in the central kiloparsec of the galaxy disc. The observed ionized gas parameters (morphology, kinematics and ionization state) can be explained by a gas outflow above the plane of the galaxy caused by a star formation in the circumnuclear region. Galactic wind parameters in NGC 4460: outflow velocity, total kinetic energy - are several times smaller comparing with the known galactic wind in NGC 253, which is explained substantially lower total star formation rate."

Ionized gas in the starburst core and halo of NGC 1140
Authors: M. S. Westmoquette, J. S. Gallagher III, L. de Poitiers, arXiv:1001.0698 [ps, pdf, other]
Comments: 13 pages, 9 figures (6 colour). Accepted for publication in MNRAS

Supernova Remnants and the Interstellar Medium of M83: Imaging & Photometry with WFC3 on HST
Authors: Michael A. Dopita, et al, arXiv:1001.0815 [pdf, other]
Comments: Accepted for publication in Astrophysical Journal. 10 figures, 41 pp

Are galactic coronae thermally unstable?
Authors: Carlo Nipoti, arXiv:1001.1246 [ps, pdf, other]
Comments: 4 pages, to appear in "Hunting for the Dark: The Hidden Side of Galaxy Formation", Malta, 19-23 Oct. 2009, eds. V.P. Debattista & C.C. Popescu, AIP Conf. Ser

A lower limit of 50 microgauss for the magnetic field near the Galactic Centre
Authors: Roland M. Crocker, David Jones, Fulvio Melia, Jürgen Ott, Raymond J. Protheroe
Comments: Published in Nature. 17 page main article; 4 figures, arXiv:1001.1275 [pdf, other]
Journal-ref: Nature 468, 7277, p65, 2010

Unveiling the Sigma-Discrepancy in IR-Luminous Mergers I: Dust & Dynamics
Authors: Barry Rothberg, Jacqueline Fischer, arXiv:1001.1309 [ps, pdf, other]
Comments: Accepted for publication in The Astrophysical Journal. 82 pages, 19 Figures, 2 Appendice

Variations in Integrated Galactic Initial Mass Functions due to Sampling Method and Cluster Mass Function
Authors: M. R. Haas, P. Anders, arXiv:1001.2009 [ps, pdf, other]
Comments: Resubmitted to A&A, 14 pages, 9 Figures

From their abstract: "If the integrated galactic initial mass function originates from stars formed in clusters, the IGIMF could be steeper than the IMF. We investigate how well constrained this steepening is and how it depends on the choice of sampling method and CMF. We compare analytic sampling to several implementations of random sampling of the IMF, and different CMFs. ... As we still do not understand the details of star formation, one sampling method cannot be favoured over another. Also, the CMF at very low cluster masses is not well constrained observationally. These uncertainties need to be taken into account when using an IGIMF, with severe implications for galaxy evolution models and interpretations of galaxy observations."

The Recent Star Formation History of NGC 5102
Authors: Sylvie F. Beaulieu, Kenneth C. Freeman, Sebastian L. Hidalgo, Colin A. Norman, Peter J. Quinn, arXiv:1001.2236 [ps, pdf, other]
Comments: 36 pages, 16 figures, accepted in AJ

The mode of gas accretion onto star-forming galaxies
Authors: F. Marinacci, J. Binney, F. Fraternali, C. Nipoti, L. Ciotti, P. Londrillo, arXiv:1001.2446 [ps, pdf, other]
Comments: 12 pages, 8 figures, 1 table. Accepted for publication in MNRAS

Their abstract: "It is argued that galaxies like ours sustain their star formation by transferring gas from an extensive corona to the star-forming disc. The transfer is effected by the galactic fountain -- cool clouds that are shot up from the plane to kiloparsec heights above the plane. The Kelvin-Helmholtz instability strips gas from these clouds. If the pressure and the the metallicity of the corona are high enough, the stripped gas causes a similar mass of coronal gas to condense in the cloud's wake. Hydrodynamical simulations of cloud-corona interaction are presented. These confirm the existence of a critical ablation rate above which the corona is condensed, and imply that for the likely parameters of the Galactic corona this rate lies near the actual ablation rate of clouds. In external galaxies trails of HI behind individual clouds will not be detectable, although the integrated emission from all such trails should be significant. Parts of the trails of the clouds that make up the Galaxy's fountain should be observable and may account for features in targeted 21-cm observations of individual high-velocity clouds and surveys of Galactic HI emission. Taken in conjunction with the known decline in the availability of cold infall with increasing cosmic time and halo mass, the proposed mechanism offers a promising explanation of the division of galaxies between the blue cloud to the red sequence in the colour-luminosity plane. "

Interesting. I must take a closer look at the necessary conditions for the mass-loading of the local corona due to stripped gas from the clouds to cause coronal condensation.

Black Holes, AGN and other compact accreting objects

In-depth studies of the NGC 253 ULXs with XMM-Newton: remarkable variability in ULX1, and evidence for extended coronae
Authors: R. Barnard, arXiv:1001.0870 [ps, pdf, other]
Comments: Accepted for publication in MNRAS. 7 pages, 5 figures

Cold and Warm Gas Outflows in Radio AGN
Authors: Raffaella Morganti, Joanna Holt, Clive Tadhunter, Tom Oosterloo, arXiv:1001.2389 [ps, pdf, other]
Comments: Invited talk, to appear in the Proceedings of the IAU Symposium 267, "Co-Evolution of Central Black Holes and Galaxies", B.M. Peterson, R.S. Somerville, T. Storchi-Bergmann, eds., in press

From their abstract: "Clear evidence for AGN-induced outflows have been found for the majority of these young radio sources. The outflows are detected both in (warm) ionized as well in (cold) atomic neutral gas and they are likely to be driven (at least in most of the cases) by the interaction between the expanding jet and the medium. The mass outflow rates of the cold gas (HI) appear to be systematically higher than those of the ionized gas. The former reach up to ~50 Msun/yr, and are in the same range as "mild" starburst-driven superwinds in ULIRGs, whilst the latter are currently estimated to be a few solar masses per year. However, the kinetic powers associated with these gaseous outflow are a relatively small fraction (a few x 10^-4) of the Eddington luminosity of the galaxy. Thus, they do not appear to match the requirements of the galaxy evolution feedback models."

Inflows and outflows in nearby active galactic nuclei from integral field spectroscopy
Authors: Thaisa Storchi-Bergmann, arXiv:1001.2480 [ps, pdf, other]
Comments: 8 pages, 4 figures, to be published in the Proceedings of the IAU Symposium no. 267, eds. B.M. Peterson, R.S. Somerville and T. Storchi-Bergmann, 2010

Stars, Supernovae and Planets

Supernova 2007bi as a pair-instability explosion
Authors: A. Gal-Yam, et al, arXiv:1001.1156 [ps, pdf, other]
Comments: Accepted version of the paper appearing in Nature, 462, 624 (2009), including all supplementary information
Journal-ref: Nature 462 624 (2009)

Second generation planets
Authors: Hagai B. Perets, arXiv:1001.0581 [ps, pdf, other]
Comments: 8 pages. Comments are most welcome

Self-consistent Simulations of Alfven Wave Driven Winds from the Sun and Stars
Authors: Takeru K. Suzuki, arXiv:1001.2400 [ps, pdf, other]
Comments: 26 pages, 12 figures, submitted to special issue (BUKS 2009) of Space Science Review

H II regions: Witnesses to massive star formation
Authors: Thomas Peters, Robi Banerjee, Ralf S. Klessen, Mordecai-Mark Mac Low, Roberto Galvan-Madrid, Eric Keto, arXiv:1001.2470 [pdf, other]
Comments: ApJ in press
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Galaxy Astrophysics (astro-ph.GA)

Nice simulations.

Other

Pointing the SOFIA Telescope
Authors: Michael A. K. Gross, John J. Rasmussen, Elizabeth M. Moore, arXiv:1001.0197 [ps, pdf, other]
Comments: 4 pages, 3 figures. To appear in Proc. ADASS XIX (Sapporo, Japan, 2009)

The International X-ray Observatory - RFI#1
Authors: Jay Bookbinder (on behalf of the IXO Study Coordination Group, Science Definition Team, Instrument Working Group, and Telescope Working Group), arXiv:1001.2329 [pdf]
Comments: 19 pages, submitted in response to Astro2010 Decadal Program Prioritization Panel First Request for Information

Contains a nice summary of the unique science capabilities of IXO, along with a variety of interesting hardware and other technical information. Anticipated lauch date 2021. Good luck, IXO team!

Interesting Astrophysics: Dec 21 to Dec 31, 2009

2009-12-31T12:12:00.002-05:00

The final edition of Interesting Astrophysics for 2009 is as diverse as ever. Of particular note, a classic superwind in the "8 o'clock arc" at z~2.7 (Dessauges-Zavadsky et al), a sample of galaxy groups analogous to our own Local Group (Marino et al), stellar wind mass loss rates in hot stars (Lucy et al), and astrobiology (Cirkovic et al).

Galaxies and Starbursts

Galaxy Evolution in Local Group Analogs. I. A GALEX study of nearby groups
A. Marino, L. Bianchi, R. Rampazzo, L.M. Buson, D. Bettoni, arXiv:0912.4266 [ps, pdf, other]
Comments: 20 pages, 13 figures, accepted for publication in Astronomy and Astrophysics

Rest-frame ultraviolet spectrum of the gravitationally lensed galaxy `the 8 o'clock arc': stellar and interstellar medium properties
M. Dessauges-Zavadsky, S. D'Odorico, D. Schaerer, A. Modigliani, C. Tapken, J. Vernet, arXiv:0912.4384 [ps, pdf, other]

Comments: 17 pages, 10 figures, A&A, accepted

From their abstract: "We present the first detailed analysis of the rest-frame UV spectrum of the gravitationally lensed Lyman break galaxy (LBG), the `8 o'clock arc'. The spectrum of the 8 o'clock arc is rich in stellar and interstellar medium (ISM) features, and presents several similarities to the well-known MS1512-cB58 LBG. ... The ISM lines extend over ~1000 km/s and have their peak optical depth blueshifted relative to the stars, implying gas outflows of about -120 km/s. The Ly-alpha line is dominated by a damped absorption profile on top of which is superposed a weak emission, redshifted relative to the ISM lines by about +690 km/s and resulting from multiply backscattered Ly-alpha photons emitted in the HII region surrounded by the cold, expanding ISM shell."

Luminosity-Metallicity Relations for Blue Compact Dwarf Galaxies in the Optical and Near-Infrared
Yinghe Zhao, Yu Gao, Qiusheng Gu, arXiv:0912.4932 [ps, pdf, other]
Comments: 32 pages, 7 figures, accepted for publication in the Astrophysical Journal

Black Holes and AGN

Infrared Diagnostics for the Extended 12 micron Sample of Seyferts
Stefi A. Baum, Jack F. Gallimore, Christopher P. O'Dea, Catherine L. Buchanan, Jacob Noel-Storr, David J. Axon, Andy Robinson, Moshe Elitzur, Meghan Dorn, Shawn Staudaher, Martin Elvis, arXiv:0912.3545 [ps, pdf, other]

Note to self: this paper deals with the correlations within the sample, but does not name the individual members of the sample.

Numerical Astrophysics and Hydrodynamics

Self-Convergence of Radiatively Cooling Clumps
Kristopher Yirak, Adam Frank, Andrew J. Cunningham, arXiv:0912.4777 [pdf, other]
Comments: 24 pages, 7 figures. Submitted to the Astrophysical Journal

They find that a fixed number of cells per radius does not lead to convergence in simulations of radiatively cooling clumps. They present alternative prescriptions for assessing numerical convergence.

X-ray astronomy

A wide field X-ray telescope for astronomical survey purposes: from theory to practice
P. Conconi, S. Campana, G. Tagliaferri, G. Pareschi, O. Citterio, V. Cotroneo, L. Proserpio, M. Civitani, arXiv:0912.5331 [ps, pdf, other]
Comments: Submitted to MNRAS (3 table, 13 figures), comments welcome

Stars, Supernovae and Planets

Mass fluxes for hot stars
L.B. Lucy, arXiv:0912.4209 [ps, pdf, other]
Comments: Submitted to A&A; 6 pages, 5 figures; second revision

Comprehensive Photometric Histories of All Known Galactic Recurrent Novae
Bradley E. Schaefer, arXiv:0912.4426 [pdf, other]

Comments: ApJSupp in press, 273 pages, 34 tables, 71 figures

Note the size of the paper! That is definitely a labor of love.

3D simulations of supernova remnants evolution including non-linear particle acceleration
Gilles Ferrand, Anne Decourchelle, Jean Ballet, Romain Teyssier, Federico Fraschetti, arXiv:0912.4886 [ps, pdf, other]
Comments: accepted for publication in A&A (final version)

PopStar Evolutionary Synthesis Models II: Optical emission-line spectra from Giant Hii regions
M.L. Martín-Manjón, M.L. García-Vargas, M. Mollá, A.I. Díaz, arXiv:0912.4730 [ps, pdf, other]
Comments: 20 pages, 26 figures, accepted for publication in MNRAS Main Journal

Including All the Lines
Robert L. Kurucz, arXiv:0912.5371 [ps, pdf, other]
Comments: 9 pages, no figures. Presented at "Dimitrifest" conference in Boulder, Colorado, March 30 - April 3, 2009
Journal-ref: Recent Directions in Astrophysical Quantitative Spectroscopy and Radiation Hydrodynamics. Edited by I. Hubeny, J.M. Stone, K. MacGregor, and K. Werner. AIP Conference Proceedings 1171, pp. 43-51, 2009

Astrobiology

Galactic Punctuated Equilibrium: How to Undermine Carter's Anthropic Argument in Astrobiology
Milan M. Cirkovic, Branislav Vukotic, Ivana Dragicevic, arXiv:0912.4980 [pdf]
Comments: 3 figures, 26 pages
Journal-ref: Published in Astrobiology, 2009, Volume 9, Issue 5, pp. 491-501

Where is the joy in research?

2009-12-29T09:19:00.003-05:00

Dennis Overbye has a rather odd essay in the NYT: "The Joy of Physics Isn’t in the Results, but in the Search Itself ." It starts off reading as a conventional justification for pure research based on the unanticipated but fundamentally useful technological products it produces, products that applied scientific or technological research would not have produced. You know the things: hypertext and the WWW, digital camera sensors, MRI and PET scanners, Velcro, pens that write when upside down, memory foam beds.

But then it veers off to tackle, as far as I can tell, the slow and bumpy road along the path of scientific progress from Overbye's perspective as a science writer in 2009. The pre-servicing mission Hubble contrasted with post servicing mission glory, the Large Hadron Collider's commissioning woes, and the pre-announcement hype of CDMS-2's decidedly ambiguous one (or two, if you're generous) sigma pseudo result. This is more in line with the essay's title.

I presume that Overbye's point was to highlight that the scientific method is not all about predictable results that appear in a regular and preplanned way. That both the results and process of science are unpredictable, and that's where the "joy" of it lies.

Its all very well, admirable even, for a science writer to tackle societies naive and preconceived views of how science works, but I must say I think Overbye's essay veers to much in the opposite direction to ignore the many years of routine operation by telescopes (the result of careful planning and hard work) and particle colliders, where experiments are planned and go roughly as expected. Unanticipated surprises happen, but the surprise us because they're rare and contrast so vividly with the larger edifice of scientific progress built slow accumulation and refinement.

Returning to the title of Overbye essay, I'd agree that doing science is fun. Seeing or discovering things that no-one else has ever seen or thought is a thrill. The mental challenge itself is pleasurable, even when you're treading scientific ground where others have gone before. But getting a result - answering a question - even if it isn't the answer you expected, is the payoff and culmination of all the hard work. So some of the joy of physics is certainly in the search, but a lot of it is in getting results.

CDMS-2's 1-sigma dark matter result.

2009-12-18T12:48:00.003-05:00

After much speculation the CDMS-2 "dark matter detection result" announced yesterday turns out to be 2 events with an expected background rate of 0.8 events in the 2007-2008 time frame of the experiment (SciAm news piece).

Exactly two events would happen by chance ~14% of the time (>=2 events would happen 20% of the time), so we're basically talking about a ~1 sigma result. Meh. Hardly impressive. It'd take 10 events under a 0.8 count background rate to get me excited.

Interesting Astrophysics: Dec 07 to 18

2009-12-18T10:18:00.002-05:00

Not a white christmas but a windy one: Razoumov, Westmoquette et al, Rubin et al, Vanzella et al, Crenshaw et al, and Kobulnicky et al are all wind-related papers or preprints (and mainly on galactic winds). Another paper of particular note is Welsh et al's amazing 3-D mapping of the local neutral ISM (within 300 pc) using NaI and CaII absorption line spectroscopy toward 1857 nearby early-type stars.

Galaxies and Starbursts

Damped Lyα Absorber Kinematics and Outflows from Starburst Galaxies
Razoumov, Alexei O., 2009, The Astrophysical Journal, Volume 707, Issue 1, pp. 738-749.
PDF (1.84 MB) | HTML

VLT/FLAMES-ARGUS observations of stellar wind-ISM cloud interactions in NGC 6357
Westmoquette, M. S.; Slavin, J. D.; Smith, L. J.; Gallagher, J. S., III, 2009, MNRAS, in press
Full Text: HTML, PDF (Size: 2563K)

PAH processing in a hot gas
E. R. Micelotta, A. P. Jones, A. G. G. M. Tielens, arXiv:0912.1595 [ps, pdf, other]
Comments: 16 pages, 11 figures, accepted for publication in Astronomy and Astrophysics

From their abstract: "The PAH lifetime in a tenuous hot gas (n_H ~ 0.01 cm^-3, T ~ 10^7 K), typical of the coronal gas in galactic outflows, is found to be about thousand years, orders of magnitude shorter than the typical lifetime of such objects. Conclusions: In a hot gas, PAHs are principally destroyed by electron collisions and not by the absorption of X-ray photons from the hot gas. The resulting erosion of PAHs occurs via C_2 loss from the periphery of the molecule, thus preserving the aromatic structure. The observation of PAH emission from a million degree, or more, gas is only possible if the emitting PAHs are ablated from dense, entrained clumps that have not yet been exposed to the full effect of the hot gas."

The Persistence of Cool Galactic Winds in High Stellar Mass Galaxies Between z~1.4 and ~1
Kate H. R. Rubin, Benjamin J. Weiner, David C. Koo, Crystal L. Martin, J. Xavier Prochaska, Alison L. Coil, Jeffrey A. Newman, arXiv:0912.2343 [ps, pdf, other]
Comments: Submitted to ApJ. 25 pages, 19 figures, Figure 2 reduced in resolution. Uses emulateapj format

From their abstract: "We present an analysis of the MgII 2796, 2803 and FeII 2586, 2600 absorption line profiles in coadded spectra of 468 galaxies at 0.7 < z < 1.5. ... The outflows
have hydrogen column densities N(H) > 10^19.3 cm^-2, and extend to velocities
of ~500 km/s. While galaxies with SFR > 10 Msun/yr host strong outflows in both
this and the W09 sample, we do not detect outflows in lower-SFR (i.e., log
M_*/Msun < 10.5) galaxies at lower redshifts. Using a simple galaxy evolution
model which assumes exponentially declining SFRs, we infer that strong outflows
persist in galaxies with log M_*/Msun > 10.5 as they age between z=1.4 and z~1,
presumably because of their high absolute SFRs. Finally, using high resolution
HST/ACS imaging in tandem with our spectral analysis, we find evidence for a
weak trend (at 1 sigma significance) of increasing outflow absorption strength
with increasing galaxy SFR surface density."

The unusual NIV]-emitter galaxy GDS J033218.92-275302.7: star formation or AGN-driven winds from a massive galaxy at z=5.56
E. Vanzella, A. Grazian, M. Hayes, L. Pentericci, D. Schaerer, M. Dickinson, S. Cristiani, M. Giavalisco, A. Verhamme, M. Nonino, P. Rosati, arXiv:0912.3007 [ps, pdf, other]
Comments: 13 pages, 9 figures. Accepted for publication in Astronomy and Astrophysics

The central energy source of 70micron-selected galaxies: Starburst or AGN?
M. Symeonidis, D. Rosario, A. Georgakakis, J. Harker, E. S. Laird, M. J. Page
Comments: 20 pages, 14 figures, accepted for publication in MNRAS

It is starbursts.

Model analysis of the very high energy detections of the starburst galaxies M82 and NGC 253

E. de Cea del Pozo, D. F. Torres, A. Y. Rodriguez, O. Reimer, arXiv:0912.3497 [ps, pdf, other]
Comments: 6 pages, 3 figures, 2 tables, 2009 Fermi Symposium, eConf Proceedings C091122

Black Holes and AGN

The Geometry of Mass Outflows and Fueling Flows in the Seyfert 2 Galaxy Mrk 3
D.M. Crenshaw, S.B. Kraemer, H.R. Schmitt, Y.L. Jaffe, R.P. Deo, N.R. Collins, T.C. Fischer, arXiv:0912.2420 [ps, pdf, other]
Comments: 22 page, 7 figures, accepted for publication in the Astronomical Journal

Their abstract: We present a study of the resolved emission-line regions and an inner dust/gas disk in the Seyfert 2 galaxy Mrk 3, based on Hubble Space Telescope observations. We show that the extended narrow-line region (ENLR), spanning ~4 kpc, is defined by the intersection of the ionizing bicone of radiation from the AGN and the inner disk, which is not coplanar with the large-scale stellar disk. This intersection leads to different position and opening angles of the ENLR compared to the narrow-line region (NLR). A number of emission-line arcs in the ENLR appear to be continuations of dust lanes in the disk, supporting this geometry. The NLR, which consists of outflowing emission-line knots spanning the central ~650 pc, is in the shape of a backwards S. This shape may arise from rotation of the gas, or it may trace the original fueling flow close to the nucleus that was ionized after the AGN turned on."

Stars, Supernovae and Planets

OB Stars & Stellar Bowshocks in Cygnus-X: A Novel Laboratory Estimating Stellar Mass Loss Rates
Henry A. Kobulnicky, Ian J. Gilbert, Daniel C. Kiminki, arXiv:0912.1314 [ps, pdf, other]
Comments: 49 pages, 19 figures; Accepted for publication in ApJ; full-resolution color figure version available at this http URL; comments invited

CoRoT-7 b: Super-Earth or Super-Io?
Rory Barnes, Sean N. Raymond, Richard Greenberg, Brian Jackson, Nathan A. Kaib, arXiv:0912.1337 [ps, pdf, other]
Comments: 13 pages, 3 figures, accepted to ApJ Letters

The simultaneous formation of massive stars and stellar clusters
Rowan J. Smith, Steven Longmore and Ian Bonnell, 2009, MNRAS, 400, 1775
Full Text: HTML, PDF (Size: 20619K)

Updated stellar yields from Asymptotic Giant Branch models
Amanda I. Karakas, arXiv:0912.2142 [ps, pdf, other]
Comments: Accepted for publication in MNRAS; 15 pages

New 3-D gas density maps of NaI and CaII interstellar absorption within 300pc
Barry Y. Welsh, Rosine Lallement, Jean-Luc Vergely, Severine Raimond, arXiv:0912.3040 [ps, pdf, other]
Comments: A&A accepted

The NaI and CaII distributions are quite different. A very impressive piece of work.

Numerical Methods and Theoretical Astrophysics

Astrophysical turbulence
Axel Brandenburg, Aake Nordlund, arXiv:0912.1340 [ps, pdf, other]

Comments: 80 pages, 24 figures, submitted to Reports on Progress in Physics. For higher figure quality and more frequent revisions see this http URL

Detailed Decomposition of Galaxy Images. II. Beyond Axisymmetric Models
Chien Y. Peng, Luis C. Ho, Chris D. Impey, Hans-Walter Rix, arXiv:0912.0731 [ps, pdf, other]

Comments: 41 pages, 22 figures, AJ submitted. Comments welcomed. Full resolution version of this paper is available at: this http URL

Dynamical Models for the Formation of Elephant Trunks in H II Regions
Jonathan Mackey, Andrew J. Lim, arXiv:0912.1499 [ps, pdf, other]

Comments: 19 pages, 11 figures, accepted for publication in MNRAS. Version with high resolution figures available at this http URL

XMM-Newton AO-9 accepted proposals announced

2009-12-15T09:54:00.002-05:00

Speaking of XMM-Newton, the results of AO-9 observing proposal round have just been made available.

The list of XMM-Newton proposals accepted by the AO-9 Observing Time
Allocation Committee (OTAC) and associated proposal abstracts are
available at:

http://xmm.esac.esa.int/external/xmm_news/otac_results/ao9_results/

The Principal Investigators of submitted proposals have been informed
about the results of the OTAC evaluation by e-mail. The e-mail
contains the details about the second phase proposal submission for
successful observations, which will need to be done via the XMM-Newton
Remote Proposal Submission System (XRPS). The XRPS will be closed on
the 5th of February 2010 at 13:00 UT.

AO-9 observations will start to be routinely performed in May 2010.

Happy 10th birthday, XMM-Newton

2009-12-10T09:37:00.003-05:00

From the XMM-Newton mailing list:

10 Years in Orbit: HAPPY BIRTHDAY, XMM-Newton!

Today, XMM-Newton is celebrating its 10th anniversary. On the 10th of
December 1999 at 14:32 GMT the European Space Agency's XMM-Newton
observatory was launched and started exploring the wonders of the
X-ray universe.

During its first decade of operations, XMM-Newton has supplied new
data to every aspect of astronomy, improving our understanding from
nearby comets to the most distant quasars and gamma-ray bursts.

A dedicated web site celebrating this event is available at:

http://xmm.esac.esa.int/external/xmm_news/items/10th_Anniversary/

We wish all the best to XMM-Newton for the years to come.

We take this opportunity to thank you all for your continued support
and interest in the mission.

The ESA website for XMM-Newton produced the highlights poster shown above (higher resolution versions available here). Of course M82, everyone's favorite starburst galaxy with a galactic wind, features prominently.

Interesting Astrophysics: Nov 23 to Dec 04, 2009

2009-12-04T09:31:00.002-05:00

In honor of the Thanksgiving Day Holiday here in the US the preprint server has produced a veritable feast of interesting papers over the last two weeks.

Of particular note are the following.

Radio spectra of everyone's favorite starbursts galaxies: M82, NGC 253 and Arp 220 (Williams & Bower). Cosmological N-body/SPH simulations affirming the importance of galactic winds, only not quite in the normal way (Oppenheimer et al).

An apparently physically large (6+ kpc) and powerful wind in the AGN SDSS J0318-0600 (Dunn et al), but note that... Krug et al find that AGN probably do not play a significant role in driving the outflows from most Seyfert galaxies, except possibly the high velocity outflows in some Seyfert 1s. Camus et al and Falceta-Goncalves et al have interesting, but very different, simulations of filamentary structures in the Crab Nebula and NGC 1275 respectively (The HST press release image of NGC 1275 [Fabian et al] is shown above).

Sadakane et al find high velocity narrow Na I absorption lines in the spectrum of Nova V1280 Sco. Bowler et al find that massive planets appear significantly more common around A stars than G stars.

Galaxies and Starbursts

The properties of the stellar populations in ULIRGs II: the star formation histories and evolution
Javier Rodriguez-Zaurin, C.N. Tadhunter, R.M. Gonzalez-Delgado, arXiv:0911.4052 [ps, pdf, other]
Comments: Accepted for publication in MNRAS. The paper contains 16 pages, 6 figures and 7 tables

GALEX Ultraviolet Imaging of Dwarf Galaxies and Star Formation
Deidre A. Hunter, Bruce G. Elmegreen, Bonnie C. Ludka, arXiv:0911.4319 [ps, pdf, other]
Comments: 28 pages, 22 figures, 7 tables, to be published in Astronomical Journal

Forty Years of Research on Isolated Galaxies
J. W. Sulentic, arXiv:0911.5663 [ps, pdf, other]
Comments: 8 pages - to appear in the proceedings of 'Galaxies in Isolation: Exploring Nature vs. Nurture', held in Granada, Spain 12-15 May 2009. Editors: L. Verdes-Montenegro, A. del Olmo and J. Sulentic. PASP Conference Series

Evaluating the Calorimeter Model with Broadband, Continuous Spectra of Starburst Galaxies Observed with the Allen Telescope Array
Peter K. G. Williams, Geoffrey C. Bower, arXiv:0912.0014 [ps, pdf, other]
Comments: 44 pages, 15 figures, ApJ accepted

Their abstract: "Although the relationship between the far-infrared and cm-wave radio luminosities of normal galaxies is one of the most striking correlations in astronomy, a solid understanding of its physical basis is lacking. In one interpretation, the "calorimeter model," rapid synchrotron cooling of cosmic ray electrons is essential in reproducing the observed linear relationship. Observed radio spectra, however, are shallower than what is expected of cooled synchrotron emission. In Thompson et al. (2006), a simple parameterized model is presented to explain how relatively shallow observed spectra might arise even in the presence of rapid synchrotron cooling by accounting for ionization losses and other cooling mechanisms. During the commissioning of the 42-element Allen Telescope Array, we observed the starburst galaxies M82, NGC 253, and Arp 220 at frequencies ranging from 1 to 7 GHz, obtaining unprecedented broadband continuous radio spectra of these sources. We combine our observations with high-frequency data from the literature to separate the spectra into thermal and nonthermal components. The nonthermal components all steepen in the cm-wave regime and cannot be well-modeled as simple power laws. The model of Thompson et al. is consistent with our M82 results when plausible parameters are chosen, and our results in fact significantly shrink the space of allowed model parameters. The model is only marginally consistent with our NGC 253 data. Assuming the Thompson et al. model, a steep electron energy injection index of p = -2.5 is ruled out in M82 and NGC 253 to >99% confidence. We describe in detail the observing procedures, calibration methods, analysis, and consistency checks used for broadband spectral observations with the Allen Telescope Array."

Feedback and Recycled Wind Accretion: Assembling the z=0 Galaxy Mass Function
Benjamin D. Oppenheimer, Romeel Davé, Dušan Kereš, Mark Fardal, Neal Katz, Juna A. Kollmeier, David H. Weinberg, arXiv:0912.0519 [ps, pdf, other]
Comments: 15 pages, 6 figures, submitted to MNRAS

Black Holes & AGN

The Quasar Outflow Contribution to AGN Feedback: VLT Measurements of SDSS J0318-0600
Jay P. Dunn, Manuel A. Bautista, Nahum Arav, Maxwell Moe, Kirk T. Korista, Elisa Costantini, Chris Benn, Sara Ellison, Doug Edmonds, arXiv:0911.3896 [ps, pdf, other]
Comments: Accepted for publication in ApJ, 57 pages, 14 figures

From their abstract: "Due to the uncertainty in the location of the dust extinction, we arrive at two viable distances for the main ouflow component from the central source, 6 and 18 kpc, where we consider the 6 kpc location as somewhat more physically plausable. Assuming the canonical global covering of 20% for the outflow and a distance of 6 kpc, our analysis yields a mass flux of 120 M_sun yr^-1 and a kinetic luminosity that is ~0.1% of the bolometric luminosity of the object. Should the dust be part of the outflow, then these values are ~4x larger. The large mass flux and kinetic luminosity make this outflow a significant contributor to AGN feedback processes."

Neutral Gas Outflows and Inflows in Infrared-Faint Seyfert Galaxies
Hannah B. Krug, David S. N. Rupke, Sylvain Veilleux, arXiv:0911.3897 [ps, pdf, other]
Comments: 50 pages, 12 figures, accepted for publication in ApJ

From their abstract: "The present paper describes the results from a search for outflows in 35 infrared-faint Seyferts with 10^9.9 < L_IR/L_sun < 10^11, or, equivalently, star formation rates (SFR) of ~0.4 -- 9 solar masses per year, to attempt to isolate the source of the outflow. We find that the outflow detection rates for the infrared-faint Seyfert 1s (6%) and Seyfert 2s (18%) are lower than previously reported for infrared-luminous Seyfert 1s (50%) and Seyfert 2s (45%). The outflow kinematics of infrared-faint and infrared-bright Seyfert 2 galaxies resemble those of starburst galaxies, while the outflow velocities in Seyfert 1 galaxies are significantly larger. Taken together, these results suggest that the AGN does not play a significant role in driving the outflows in most infrared-faint and infrared-bright systems, except the high-velocity outflows seen in Seyfert 1 galaxies."

Radiation-Driven Outflows in Active Galactic Nuclei
Daniel Proga, Ryuichi Kurosawa, arXiv:0912.0565 [ps, pdf, other]
Comments: 9 pages, 5 figures, in Recent Directions In Astrophysical Quantitative Spectroscopy And Radiation Hydrodynamics: Proceedings of the International Conference in Honor of Dimitri Mihalas for His Lifetime Scientific Contributions on the Occasion of His 70th Birthday (AIP Conference Proceedings 1171)

Interstellar Medium / Hydrodynamics

Flows along cometary tails in the Helix planetary nebula NGC 7293
John Meaburn, Panos Boumis, arXiv:0911.4843 [ps, pdf, other]
Comments: 8 pages, 4 figures, accepted for publication in MNRAS

Properties of extra-planar HI clouds in the outer part of the Milky Way
L. Dedes, P.W.M Kalberla, arXiv:0911.4839 [ps, pdf, other]
Comments: 9 pages, 5 figures, 3 tables, Accepted for publication in A&A

Observations of 'wisps' in magnetohydrodynamic simulations of the Crab Nebula
N. F. Camus, S. S. Komissarov, N. Bucciantini and P. A. Hughes, 2009, MNRAS, 400, 1241
Full Text: HTML, PDF (Size: 7435K)

Turbulence and the formation of filaments, loops and shock fronts in NGC 1275 in the Perseus Galaxy Cluster
D. Falceta-Goncalves, E. M. de Gouveia Dal Pino, J. S. Gallagher, A. Lazarian, arXiv:0912.0545 [ps, pdf, other]
Comments: accepted by ApJ Letters

X-ray Astronomy

Methods for Estimating Fluxes and Absorptions of Faint X-ray Sources
Konstantin V. Getman, Eric D. Feigelson, Patrick S. Broos, Leisa K. Townsley, Gordon P. Garmire, arXiv:0912.0202 [ps, pdf, other]
Comments: Accepted for publication in The Astrophysical Journal. 39 pages, 15 figures

Stars, Supernovae and Planets

Introduction to nuclear astrophysics
Christian Iliadis, arXiv:0911.3965 [ps, pdf, other]
Comments: Proceedings of the 5th European Summer School on Experimental Nuclear Astrophysics, Santa Tecla, Italy, 2009, 20 pages, 4 figures, 1 table

Molecular Clouds as a Probe of Cosmic-Ray Acceleration in a Supernova Remnant
Yutaka Fujita, Yutaka Ohira, Shuta J. Tanaka, Fumio Takahara, arXiv:0911.4482 [ps, pdf, other]
Comments: Accepted for publication in ApJ Letters

Discovery of Multiple High-Velocity Narrow Circumstellar Na I D Lines in Nova V1280 Sco
Kozo Sadakane, Akito Tajitsu, Sahori Mizoguchi, Akira Arai, Hiroyuki Naito, arXiv:0911.5229 [ps, pdf, other]
Comments: Accepted for PASJ letter, 5 pages, 8 figures

Retired A Stars and Their Companions. III. Comparing the Mass-Period Distributions of Planets Around A-Type Stars and Sun-Like Stars
Brendan P. Bowler, John Asher Johnson, Geoffrey W. Marcy, Gregory W. Henry, Kathryn M. G. Peek, Debra A. Fischer, Kelsey I. Clubb, Michael C. Liu, Sabine Reffert, Christian Schwab, Thomas B. Lowe, arXiv:0912.0518 [ps, pdf, other]
Comments: Accepted by the Astrophysical Journal; 15 pages, 15 figures

From their abstract: "Thus, the properties of planets around A stars are markedly different than those around Sun-like stars, suggesting that only a small (~ 50%) increase in stellar mass has a large influence on the formation and orbital evolution of planets."

Other

A Multilingual on-line Dictionary of Astronomical Concepts
M. Heydari-Malayeri, arXiv:0911.4687 [pdf]

Comments: 3 pages, Interactive dictionary of Astronomy and Astrophysics, see: this http URL

BBC discusses costs of ESA Cosmic Vision contenders

2009-12-02T08:53:00.003-05:00

An article on the BBC by Jonathan Amos discusses the contenders for the two slots in ESA's Cosmic Visions program for 2017-2018 launches. Interestingly the article's focus is on the costs (see graph taken from article), but it also has a nice description of each mission (many of which I hadn't heard of).

The missions, and my shorter summary of their nature and aims, are:

SPICA: Joint ESA/JAXA infrared space telescope (5 to 210 micron wavelength range) with a 3.5m primary mirror.
Euclid: Map mass distributions using baryonic acoustic oscillations and weak lensing.
PLATO: A planet hunter with a particular emphasis on finding Earth-like and super-earth terrestrial planets using milli-magnitude accuracy photometry.
Solar Orbiter: Study the Sun and Solar wind from a relatively close-in orbit (as close as 48 Solar radii, it claims).
Marco Polo: Joint ESA/JAXA sample return mission from a near-earth asteroid. Note the high cost!
Cross-Scale: Study MHD plasma properties in the terrestrial magnetosphere and bow shock. 7 ESA spacecraft forming 2 nested tetrahedra with a shard corner. (International collaboration will produce the optimum fleet of 12 spacecraft in 3 nested tetrahedra.) High cost!

Interesting Astrophysics: Nov 16 to 20

2009-11-20T08:55:00.002-05:00

Its a quiet week in terms of interesting papers and preprints. Given the small number of papers no added introduction to them is necessary.

Galaxies and Starbursts

On the interstellar medium and star formation demographics of galaxies in the local universe
Matthew S. Bothwell, Robert C. Kennicutt Jr, and Janice C. Lee, 2090, MNRAS, 400, 154
Full Text: HTML, PDF (Size: 1632K)

Photodissociation chemistry footprints in the Starburst galaxy NGC 253
Sergio Martin, J. Martin-Pintado, S. Viti, arXiv:0911.2673 [ps, pdf, other]
Comments: 32 pages, 4 figures, Published in ApJ
Journal-ref: 2009 ApJ 706 1323-1330

Origin(s) of the Highly Ionized High-Velocity Clouds Based on Their Distances
N. Lehner, J. C. Howk, arXiv:0911.2732 [ps, pdf, other]
Comments: Submitted to the ApJ Letters

Black Holes and AGN

Quasar Outflow Contribution to AGN Feedback: Observations of QSO SDSS J0838+2955
Maxwell Moe, Nahum Arav, Manuel A. Bautista, Kirk T. Korista, arXiv:0911.3332 [ps, pdf, other]
Comments: 28 pages, 7 figures, 4 tables, published in Astrophysical Journal
Journal-ref: 2009 ApJ 706 525-534

Their full abstract: "We present a detailed analysis of the Astrophysical Research Consortium 3.5 m telescope spectrum of QSO SDSS J0838+2955. The object shows three broad absorption line (BAL) systems at 22,000, 13,000, and 4900 km s^-1 blueshifted from the systemic redshift of z=2.043. Of particular interest is the lowest velocity system that displays absorption from low-ionization species such as Mg II, Al II, Si II, Si II*, Fe II and Fe II*. Accurate column densities were measured for all transitions in this lowest velocity BAL using an inhomogeneous absorber model. The ratio of column densities of Si II* and Fe II* with respect to their ground states gave an electron number density of log n_e (cm^-3) = 3.75 +/- 0.22 for the outflow. Photoionization modeling with careful regards to chemical abundances and the incident spectral energy distribution predicts an ionization parameter of log U_H = -1.93 +/- 0.21 and a hydrogen column density of log N_H (cm^-2) = 20.80 +/- 0.28. This places the outflow at 3.3+1.5-1.0 kpc from the central AGN. Assuming that the fraction of solid angle subtended by the outflow is 0.2, these values yield a kinetic luminosity of (4.5+3.1-1.8) x 10^45 erg s^-1, which is (1.4+1.1-0.6)% the bolometric luminosity of the QSO itself. Such large kinetic luminosity suggests that QSO outflows are a major contributor to AGN feedback mechanisms."

Numerical Astrophysics and Hydrodynamics

Turbulence modeling and the physics of the intra-cluster medium
L. Iapichino, A. Maier, W. Schmidt, J. C. Niemeyer, arXiv:0911.2629 [ps, pdf, other]
Comments: To appear in the proceedings of the "Invisible Universe International Conference"

Characterizing Magnetohydrodynamic Turbulence in the Small Magellanic Cloud
Blakesley Burkhart, Snezana Stanimirovic, Alex Lazarian, Grzegorz Kowal, arXiv:0911.3652 [ps, pdf, other]

Stars, Supernovae and Planets

A Feature Movie of SiO Emission 20-100 AU from the Massive Young Stellar Object Orion Source I
L. D. Matthews, L. J. Greenhill, C. Goddi, C. J. Chandler, E. M. L. Humphreys, M. Kunz, rXiv:0911.2473 [pdf, other]

Comments: Accepted to ApJ (January 2010); a full resolution version along with two accompanying GIF movies may be found at this http URL

An Unusually Fast-Evolving Supernova
Dovi Poznanski, Ryan Chornock, Peter E. Nugent, Joshua S. Bloom, Mohan Ganeshalingam, Douglas C. Leonard, Weidong Li, Rollin C. Thomas, arXiv:0911.2699 [pdf, other]
Comments: Science in press, first published online on Nov 5, 2009 in Science Express. Includes supporting online materia

The low-mass Initial Mass Function in the 30 Doradus starburst cluster
M. Andersen, H. Zinnecker, A. Moneti, M. J. McCaughrean, B. Brandl, W. Brandner, G. Meylan, D. Hunter, arXiv:0911.2755 [ps, pdf, other]
Comments: Accepted in ApJ. Abstract abridged

How Common are Extrasolar, Late Heavy Bombardments?
Mark Booth, Mark C. Wyatt, Alessandro Morbidelli, Amaya Moro-Martín, Harold F. Levison, arXiv:0911.3271 [ps, pdf, other]
Comments: 2 pages, 1 figure. Contribution to the conference proceedings for 'Pathways towards habitable planets'

Other

A Vigorous Explorer Program
Martin Elvis, et al, arXiv:0911.3383 [pdf]
Comments: 18 pages, no figures. An Activities/Program White Paper submitted to the Astro2010 NAS/NRC Decadal Review of Astronomy and Astrophysics

Interesting Astrophysics: Nov 09 to 13

2009-11-13T08:56:00.002-05:00

A mixed set of interesting preprints this week, with a strong emphasis on winds, either supernova-driven winds starbursts at high redshift (Kornei et al) or possibly from the center of our own galaxy (Law), and even outflows driven by black holes (King).

A second theme with a strong showing of interesting papers is astrobiology: the biological effects of radiation from "normal" stellar processes on the main sequence (Cuntz et al) or from Gamma ray bursts (Martin et al).

Galaxies and Starbursts

Morphologies of local Lyman break galaxy analogs II: A Comparison with galaxies at z=2-4 in ACS and WFC3 images of the Hubble Ultra Deep Field
R.A. Overzier, T.M. Heckman, D. Schiminovich, A. Basu-Zych, T. Goncalves, D.C. Martin, R.M. Rich, arXiv:0911.1279 [ps, pdf, other]

Comments: Submitted to ApJ (14 pages, 7 figures). For a high-resolution colour version and background material, see this http URL

The Relationship Between Stellar Populations and Lyman Alpha Emission in Lyman Break Galaxies
Katherine A. Kornei, Alice E. Shapley, Dawn K. Erb, Charles C. Steidel, Naveen A. Reddy, Max Pettini, Milan Bogosavljevic, arXiv:0911.2000 [ps, pdf, other]
Comments: 24 pages, 15 figures, submitted to ApJ

From their abstract: "We accordingly conclude that, within the LBG sample, objects with strong Lya emission represent a later stage of galaxy evolution in which supernovae-induced outflows have reduced the dust covering fraction. We also examined the hypothesis that the attenuation of Lya photons is lower than that of the continuum, as proposed by some, but found no evidence to support this picture."

A Multiwavelength View of a Mass Outflow from the Galactic Center
C. J. Law, arXiv:0911.2061 [pdf, other]
Comments: Accepted to ApJ. 15 pages, 8 (compressed) figures

From the abstract: "I compare the physical conditions of the GC lobe to several models and find best agreement with the canonical starburst outflow model. The formation of the GC lobe is consistent with the currently observed pressure and star formation rate in the central tens of parsecs of our Galaxy. Outflows of this scale are more typical of dwarf galaxies and would not be easily detected in nearby spiral galaxies. Thus, the existence of such an outflow in our own Galaxy may indicate that it is relatively common phenomenon in the nuclei of spiral galaxies."

Black Holes and AGN

Discovery of a 115 Day Orbital Period in the Ultraluminous X-ray Source NGC 5408 X-1
Tod E. Strohmayer, arXiv:0911.1339 [ps, pdf, other]
Comments: Accepted for Publication in the Astrophysical Journal Letters

Black Hole Outflows
A.R. King, arXiv:0911.1639 [ps, pdf, other]
Comments: MNRAS, to appear

Numerical Astrophyics

Generating on-the-fly large samples of theoretical spectra through N-dimensional grid
Ching-Wa Yip, arXiv:0911.1280 [ps, pdf, other]
Comments: 7 pages, 5 figures, 1 table. Accepted for publication in AJ

Stars, Supernovae and Planets

Biological Damage due to Photospheric, Chromospheric and Flare Radiation in the Environments of Main-Sequence Stars
M. Cuntz, E. F. Guinan, R. L. Kurucz, arXiv:0911.1982 [ps, pdf, other]
Comments: 8 pages, 4 figues, Planetary Systems as Potential Sites for Life, Invited Paper, IAU Symposium 264, eds. A. Kosovichev et al. (San Francisco: Astr. Soc. Pac.), in press

Effects of Gamma Ray Bursts in Earth Biosphere
Osmel Martin, Rolando Cardenas, Mayrene Guimaraes, Liuba Penate, Jorge Horvath, Douglas Galante, arXiv:0911.2196 [pdf, other]
Comments: Accepted for publication in Astrophysics & Space Science

Interesting Astrophysics: Nov 02 to Nov 06

2009-11-06T09:05:00.002-05:00

Of particular note this week are Crighton et al (who suggest a particular case of intergalactic metal line absorption can be associated with a z=0.2272 galaxy polluting a region ~200 kpc in radius), Bertone et al (metal line cooling from the IGM predicted in the OWLS simulations) Risaliti & Elvis (a line driven model for AGN winds), and Bond et al (terrestrial planet formation models that correctly predict the observed elemental abundances also predict that terrestrial planets form wet and do not need significant water delivery from comets).

Galaxies and Starbursts

Searching for Evidence of Energetic Feedback in Distant Galaxies: A Galaxy Wide Outflow in a z~2 Ultraluminous Infrared Galaxy
D.M. Alexander, A.M. Swinbank, I. Smail, R. McDermid, N. Nesvadba, arXiv:0911.0014 [ps, pdf, other]
Comments: 10 pages, 5 figures, 1 table. Resubmitted to MNRAS after taking account of referees feedback

Galaxies at Redshift ~0.5 Around Three Closely Spaced Quasar Sightlines
Neil H. M. Crighton, Simon L. Morris, Jill Bechtold, Robert A. Crain, Buell T. Jannuzi, Allen Shone, Tom Theuns, arXiv:0911.0368 [pdf, other]
Comments: 45 pages, 21 figures. Accepted by MNRAS

From their abstract: "We identify a galaxy at z=0.2272 with associated metal absorption in two sightlines, each 200 kpc away. By constraining the star formation history of the galaxy, we show the gas causing this metal absorption may have been enriched and ejected by the galaxy during a burst of star formation 2 Gyr ago."

Enhanced Dense Gas Fraction in Ultra-Luminous Infrared Galaxies
S. Juneau, D. T. Narayanan, J. Moustakas, Y. L. Shirley, R. S. Bussmann, R. C. Kennicutt Jr, P. A. Vanden Bout, arXiv:0911.0413 [ps, pdf, other]
Comments: 20 pages, 10 figures. To be published in The Astrophysical Journal (accepted)

Black Holes and AGN

Comparison between the Luminosity functions of X-ray and [OIII] selected AGN
I. Georgantopoulos, A. Akylas, arXiv:0911.0102 [ps, pdf, other]

Comments: 7 pages to appear in Astronomy & Astrophysics

A non-hydrodynamical model for acceleration of line-driven winds in Active Galactic Nuclei
G. Risaliti, M. Elvis, arXiv:0911.0958 [ps, pdf, other]
Comments: 15 pages, 9 figures. Accepted for publication in Astronomy & Astrophysics

Numerical Astrophysics

Metal-line emission from the warm-hot intergalactic medium: I. Soft X-rays
Serena Bertone, Joop Schaye, Claudio Dalla Vecchia, C.M. Booth, Tom Theuns, Robert P.C. Wiersma, arXiv:0910.5723 [ps, pdf, other]

The Enrichment of Intergalactic Medium With Adiabatic Feedback I: Metal Cooling and Metal Diffusion
Sijing Shen, James Wadsley, Gregory Stinson, arXiv:0910.5956 [ps, pdf, other]
Comments: 16 pages, 11 figures, submitted to MNRAS

Ram-pressure stripping of halo gas in disc galaxies: implications for galactic star formation in different environments
Kenji Bekki, 2009, MNRAS, 399, 2221
Full Text: HTML, PDF (Size: 4409K)

The impact of feedback on the low redshift Intergalactic Medium
Luca Tornatore, Stefano Borgani, Matteo Viel, Volker Springel, arXiv:0911.0699 [ps, pdf, other]
Comments: revised version after referee's comments

Stars, Supernovae and Planets

Making the Earth: Combining Dynamics and Chemistry in the Solar System
Jade C. Bond, Dante S. Lauretta, David P. O'Brien, arXiv:0911.0426 [ps, pdf, other]
Comments: 61 pages (including online material), 12 figures (7 in paper, 5 online). Accepted to Icarus

From their abstract: "Bulk elemental abundances based on disk equilibrium studies have been determined for the simulated terrestrial planets of O'Brien et al. (2006). These abundances are in excellent agreement with observed planetary values, indicating that the models of O'Brien et al. (2006) are successfully producing planets comparable to those of the Solar System in terms of both their dynamical and chemical properties. Significant amounts of water are accreted in the present simulations, implying that the terrestrial planets form "wet" and do not need significant water delivery from other sources. Under the assumption of equilibrium controlled chemistry, the biogenic species N and C still need to be delivered to the Earth as they are not accreted in significant proportions during the formation process."

Interesting Astrophysics: 26 Oct to 30 Oct

2009-10-30T10:03:00.002-04:00

Galaxies and Starbursts

A New Empirical Method to Infer the Starburst History of the Universe from Local Galaxy Properties
Philip F. Hopkins, Lars Hernquist, arXiv:0910.4582 [ps, pdf, other]
Comments: 21 pages, 8 figures, accepted to MNRAS

Constraining the initial mass function of stars in the Galactic Centre
Ulf Loeckmann, Holger Baumgardt, Pavel Kroupa, arXiv:0910.4960 [ps, pdf, other]
Comments: MNRAS, accepted, 8 pages, 4 figures

HI Selected Galaxies in the Sloan Digital Sky Survey I: Optical Data
Andrew A. West, Diego A. Garcia-Appadoo, Julianne J. Dalcanton, Mike J. Disney, Constance M. Rockosi, Zeljko Ivezic, Misty C. Bentz, J. Brinkmann, arXiv:0910.4965 [ps, pdf, other]
Comments: 14 pages, 8 Figures, accepted for publication in AJ. Complete tables will be available in the AJ electronic version and on the Vizier site

HI Selected Galaxies in the Sloan Digital Sky Survey II: The Colors of Gas-Rich Galaxies
Andrew A. West, Diego A. Garcia-Appadoo, Julianne J. Dalcanton, Mike J. Disney, Constance R. Rockosi, Zeljko Ivezic, arXiv:0910.4966 [ps, pdf, other]
Comments: 12 pages, 16 figures, published in AJ (138, 796); replaced Figure 16 with higher resolution version
Journal-ref: West et al. 2009, AJ, 138, 796

Numerical Astrophysics

Adaptive Mesh Fluid Simulations on GPU
Peng Wang, Tom Abel, Ralf Kaehler, arXiv:0910.5547 [ps, pdf, other]
Comments: Submitted to New Astronomy

CUDA & MPI, with what sounds like the ZEUS MHD scheme. Hardly surprising, but nice to see some effort going into exploring the use of GPU computing with hydro codes.

Stars, Supernovae and Planets

Evolution of supermassive stars as a pathway to black hole formation
Mitchell C. Begelman, arXiv:0910.4398 [ps, pdf, other]
Comments: 10 pages, 5 figures, to appear in Monthly Notices of the Royal Astronomical Society

X-ray observations of classical novae. Theoretical implications
M. Hernanz, G. Sala, arXiv:0910.4607 [ps, pdf, other]
Comments: 6 pages, review paper accepted for publication in Astronomische Nachrichten

The Nature and Nurture of Star Clusters
Bruce G. Elmegreen, arXiv:0910.4638 [ps, pdf, other]
Comments: to be published in IAUS266: Star Clusters Basic Galactic Building Blocks Throughout Time And Space, eds. Richard de Grijs and Jacques Lepine, Cambridge University Press, 11 pages

Nuclear Star Clusters
Torsten Boeker, arXiv:0910.4863 [ps, pdf, other]
Comments: invited talk at IAU Symp. 266 "Star Clusters: Galactic Building Blocks through Space and Time"

Interesting Astrophysics: Oct 12 to Oct 23

2009-10-23T08:37:00.002-04:00

This edition of Interesting Astrophysics spans an even wide range of topics than normal, from C IV in the IGM (D'Odorico et al), X-ray emission from galaxies (Laird et al, Pietsch), a variety of supernova-related preprints, to AGN feedback/outflows and other topics I've not mentioned.

Galaxies and Starbursts

An Anisotropic Propagation Model for Galactic Cosmic Rays
Iris Gebauer, Wim de Boer, arXiv:0910.2027 [ps, pdf, other]
Comments: 19 pages, 19 figures, submitted to A&A

The rise of the C IV mass density at z<2.5
Valentina D'Odorico, Francesco Calura, Stefano Cristiani, Matteo Viel, arXiv:0910.2126 [ps, pdf, other]
Comments: Paper accepted by MNRAS. The parameters of the C IV line fitting will be available in electronic format

The radial distribution of core-collapse supernovae in spiral host galaxies
A. A. Hakobyan, G. A. Mamon, A. R. Petrosian, D. Kunth, M. Turatto, arXiv:0910.1801 [ps, pdf, other]
Comments: 10 pages, 6 figures, 5 tables. Astronomy & Astrophysics, in press

On the X-ray properties of submm-selected galaxies
Elise S. Laird, Kirpal Nandra, Alexandra Pope, Douglas Scott, arXiv:0910.2464 [ps, pdf, other]
Comments: 12 pages, 5 figures, accepted for publication in MNRAS

X-ray emission from optical novae in M 31
W. Pietsch, arXiv:0910.3865 [ps, pdf, other]
Comments: 6 pages, 4 figures, accepted for publication in Aston.Nachr

Bars in Starbursts and AGNs -- A Quantitative Reexamination
Lei Hao, Shardha Jogee, Fabio D. Barazza, Irina Marinova, Juntai Shen, arXiv:0910.3960 [ps, pdf, other]
Comments: 8 pages, 3 figures, to be published in "Galaxy Evolution: Emerging Insights and Future Challenges", ed. S. Jogee et al., Astron. Soc. Pacific, 2009

From their abstract: "We find that AGN and star-forming galaxies have similar optical bar fractions, 47% and 50%, respectively. Both bar fractions are higher than that in inactive galaxies (29%)."

Extragalactic CS survey
E. Bayet, R. Aladro, S. Martin, S. Viti, J. Martin-Pintado, arXiv:0910.4282 [pdf, other]
Comments: 17 pages, 16 figures, 3 tables, Accepted to ApJ

From the abstract: "We present a coherent and homogeneous multi-line study of the CS molecule in nearby (D$<$10Mpc) galaxies. We include, from the literature, all the available observations from the $J=1-0$ to the $J=7-6$ transitions towards NGC 253, NGC 1068, IC 342, Henize~2-10, M~82, the Antennae Galaxies and M~83."

Black Holes and AGN

Feeding and Feedback in nearby AGN from Integral Field Spectroscopy
Thaisa Storchi-Bergmann, arXiv:0910.3234 [ps, pdf, other]
Comments: 4 pages, 2 figures, to appear in the proceedings of the conference "The Monster's Fiery Breath", eds. Sebastian Heinz and Eric Wilcots

From the abstract: "The ionized gas, on the other hand, traces the AGN feedback. Its
kinematics shows two components: (1) one originating in the plane, and
dominated by circular rotation; (2) another outflowing along the Narrow-Line
Region (NLR) whose flux distribution and kinematics frequently correlate with
structures seen in radio maps. Mass outflow rates along the NLR range from
10^-2 to 1 M_sun yr^-1, corresponding to 10-100 times the accretion rate to the
AGN, indicating that most of the NLR gas mass has been entrained from the
galaxy plane. The average kinetic power of the NLR outflows is ~10^-4 times the
bolometric luminosity.
"

AGN Feedback: Does it work?
Smita Mathur, Rebecca Stoll, Yair Krongold, Fabrizio Nicastro, Nancy Brickhouse, Martin Elvis, arXiv:0910.3691 [ps, pdf, other]
Comments: to appear in proceedings of the conference "The Monster's Fiery Breath: Feedback in Galaxies, Groups, and Clusters", June 2009, Madison, WI, Eds. S. Heinz & E. Wilcots

Interstellar Medium

PAH processing in interstellar shocks
E. R. Micelotta, A. P. Jones, A. G. G. M. Tielens, arXiv:0910.2461 [ps, pdf, other]
Comments: 21 pages, 11 figures, accepted for publication in Astronomy and Astrophysics

VLT/FLAMES-ARGUS observations of stellar wind--ISM cloud interactions in NGC 6357
M.S. Westmoquette, J.D. Slavin, L.J. Smith, J.S. Gallagher III, arXiv:0910.4191 [ps, pdf, other]
Comments: 9 pages, 5 figures (3 colour). Accepted for publication in MNRAS

Stars, Supernovae and Planets

The rebrightening of planetary nebulae through ISM interaction

C J Wareing, arXiv:0910.2200 [ps, pdf, other]

Comments: Review paper accepted to PASA. 8 pages, 5 figures. High resolution images available from the author

Stellar Feedback in Molecular Clouds and its Influence on the Mass Function of Young Star Clusters
S. Michael Fall, Mark R. Krumholz, Christopher D. Matzner, arXiv:0910.2238 [ps, pdf, other]
Comments: 5 pages, 2 figures, emulateapj format, submitted to ApJL

Typing Supernova Remnants Using X-ray Line Emission Morphologies
Laura A. Lopez, Enrico Ramirez-Ruiz, Carles Badenes, Daniela Huppenkothen, Tesla E. Jeltema, David A. Pooley, arXiv:0910.3208 [ps, pdf, other]
Comments: 4 pages, 1 figure, accepted for publication in ApJL

Line-of-sight Shell Structure of the Cygnus Loop
Hiroyuki Uchida, Hiroshi Tsunemi, Satoru Katsuda, Masashi Kimura, Hiroko Kosugi, Hiroaki Takahashi, arXiv:0910.3731 [ps, pdf, other]
Comments: 8 pages, 7 figures, accepted for publication in ApJ
Journal-ref: Astrophysical Journal 705 (2009) 1152-1159

Other

FISH: A 3D parallel MHD code for astrophysical applications
R. Kaeppeli, S. C. Whitehouse, S. Scheidegger, U.-L. Pen, M. Liebendoerfer, arXiv:0910.2854 [ps, pdf, other]
Comments: 27 pages, 11 figures

Astrometry.net: Blind astrometric calibration of arbitrary astronomical images
Dustin Lang, David W. Hogg, Keir Mierle, Michael Blanton, Sam Roweis, arXiv:0910.2233 [pdf, other]
Comments: submitted to AJ

A very cool idea!

Interesting Astrophysics: 05 Oct to 09 Oct

2009-10-09T08:58:00.002-04:00

A mixed bag of interesting preprints this week. Of note are local analogs of the Lyman Break Galaxies (Overzier et al), the radio-FIR correlation at high z (Lacki & Thompson), and a possible optical counterpart to an intermediate mass black hole candidate (Soria et al).

Galaxies and Starbursts

Local Lyman Break Galaxy Analogs: The Impact of Massive Star-forming Clumps on the Interstellar Medium and the Global Structure of Young, Forming Galaxies
R.A. Overzier, T.M. Heckman, C. Tremonti, L. Armus, A. Basu-Zych, T. Goncalves, R.M. Rich, D.C. Martin, A. Ptak, D. Schiminovich, H.C. Ford, B. Madore, M. Seibert, arXiv:0910.1352 [ps, pdf, other]

Comments: The Astrophysical Journal, In Press (22 pages, 16 figures). For the full version with high-resolution colour figures, see: this http URL

Stationary models for the extra-planar gas in disc galaxies
F. Marinacci, F. Fraternali, L. Ciotti, C. Nipoti, arXiv:0910.0404 [ps, pdf, other]
Comments: 14 pages, 7 figures, accepted for pubblication in MNRAS

A cloudy halo model.

The Physics of the FIR-Radio Correlation: II. Synchrotron Emission as a Star-Formation Tracer in High-Redshift Galaxies
Brian C. Lacki, Todd A. Thompson, arXiv:0910.0478 [ps, pdf, other]
Comments: Submitted to ApJ

The fundamental gas depletion and stellar-mass buildup times of star forming galaxies
Jan Pflamm-Altenburg, Pavel Kroupa, arXiv:0910.1089 [ps, pdf, other]
Comments: accepted for publication in ApJ

The WMAP haze from the Galactic Center region due to massive star explosions and a reduced cosmic ray scale height
Peter L. Biermann, Julia K. Becker, Gabriel Caceres, Athina Meli, Eun-Suk Seo, Todor Stanev, arXiv:0910.1197 [ps, pdf, other]
Comments: 10 pages

Black Holes and AGN

The Activity of the Neighbours of AGN and Starburst Galaxies: Towards an evolutionary sequence of AGN activity
E.Koulouridis, M.Plionis, V.Chavushyan, D.Dultzin, Y.Krongold, I.Georgantopoulos, C.Goudis, arXiv:0910.1355 [ps, pdf, other]
Comments: 50 pages, 5 figures, 41 spectra

Discovery of an optical counterpart to the hyperluminous X-ray source in ESO 243-49
Roberto Soria, George K. T. Hau, Alister W. Graham, Albert K. H. Kong, N. Paul M. Kuin, I-Hui Li, Ji-Feng Liu, Kinwah Wu, arXiv:0910.1356 [ps, pdf, other]
Comments: 5 pages, submitted to MNRAS Letters. Contact R Soria for higher-resolution figures

Theoretical and Numerical Astrophysics, including Cosmology

Pressure Support vs. Thermal Broadening in the Lyman-alpha Forest II: Effects of the Equation of State on Transverse Structure
Molly S. Peeples, David H. Weinberg, Romeel Davé, Mark A. Fardal, Neal Katz, arXiv:0910.0250 [ps, pdf, other]
Comments: 11 figures, submitted to MNRAS

Stars, Supernovae and Planets

Ionized Gas Towards Molecular Clumps: Physical Properties of Massive Star Forming Regions
Katharine G. Johnston, Debra S. Shepherd, James E. Aguirre, Miranda K. Dunham, Erik Rosolowsky, Kenneth Wood, arXiv:0910.0251 [ps, pdf, other]
Comments: 67 pages, 16 figures, 8 tables, accepted for publication in ApJ

From their abstract: "For clumps with associated ionized gas, the combined mass of the ionizing massive stars is compared to the clump masses to provide an estimate of the instantaneous star formation efficiency. These values range from a few percent to 25%, and have an average of 7 +/- 8%. We also find a correlation between the clump mass and the mass of the ionizing massive stars within it, which is consistent with a power law. This result is comparable to the prediction of star formation by competitive accretion that a power law relationship exists between the mass of the most massive star in a cluster and the total mass of the remaining stars."

HuffPo lunacy

2009-10-08T18:32:00.008-04:00

The Huffington Post has a certain reputation for allowing (perhaps it would be more accurate to say promoting) quacks, vaccine denialists, conspiracy theorists and other superstitious wackery, but the example that follows is impressively moronic even by HuffPo standards.

As Tariq Malik at Space.com reports regarding NASA's LCROSS lunar impact (emphasis mine):

NASA's LCROSS mission will slam a spacecraft and an empty rocket stage into the moon's south pole Friday morning at 7:31 a.m. EDT (1131 GMT) in a search for water ice buried in the perpetual shadows of lunar craters.
Scientists are eagerly awaiting the LCROSS crashes and hope they'll provide a definitive answer on whether lunar water ice could be used to support future astronauts on the moon. But at least one person — novelist and screenwriter Amy Ephron — has spoken out against the $79 million mission on her Huffington Post blog and launched a Twitter campaign ("helpsavethemoon") to save the moon from future onslaught.

"I'm not a big fan of explosions, anyway. In Iraq or Afghanistan or the South Pole of the Moon. But who does have a territorial prerogative there?" Ephron wrote. "Who has jurisdiction? Who has the right to say that it's okay to blow up a crater on the moon?"

Apparently, Mother Nature does. The moon is covered in craters, with new ones like those to be created by the LCROSS probes popping up all the time by meteorites that pummel the lunar surface.

"The image of this impact, what we're doing with the moon, is something that occurs naturally four times a month on the moon, whether we're there or not," LCROSS principal investigator Tony Colaprete told reporters Thursday.

I love Malik and Colaprete's understated but effectively utter refutation of Ephron's deliberately ignorant rant. Keep it up!

New mega ring around Saturn discovered using Spitzer

2009-10-08T09:15:00.003-04:00

Infrared observations using the Spitzer Space Telescope, published by Verbiscer et al (2009, Nature), have revealed the largest known ring around Saturn, an annulus of very tenuous material extending between 6 million and 18 million kilometers from Saturn, and tilted by 27 degree from the plane of the traditional rings (which only extend out to ~240,000 km).

The material in the new ring comes from the battered and cratered moon Phoebe. Of more interest, this new dust ring explains why the leading side of Iapetus is so much darker than the rest of it - the dark front surface of Iapetus is material from the ring swept up by Iapetus as it orbits at the inner edge of the new ring.

In truth a link between the dark front of Iapetus and Phoebe has been suspected before now, as the composition of the dark material is very similar to that of Phoebe based on near IR spectroscopy with Cassini. What the Spitzer observations reveal is the presence of the dust ring and hence the mechanism of material transfer from Phoebe to Iapetus.

Although the ring is physically huge, with a volume of ~5e21 km^3 (this is my BOTE calculation. As far as I can tell Verbiscer et al do not quote a volume), it is incredibly tenuous, and if all the material within it were collected back into one place it would possibly only occupy ~ 1 km^3 of rock, i.e. the volume of a crater on Phoebe.

The other interesting thing is that the material migrates inwards under the influence of radiation pressure. From Verbiscer et al:

On long timescales, collisions and inward transport become important. Collision with Phoebe, the dominant loss mechanism for particles larger than several centimetres in size, takes on the order of 10¹⁰ years. Re-radiation of absorbed sunlight exerts an asymmetric force on dust grains, causing them to spiral in towards Saturn with a characteristic timescale of 1.5 10⁵r_g years where r_g is the particle radius in micrometres. This force brings all centimetre-sized and smaller material to Iapetus and Titan unless mutual particle collisions occur first. The rate of mutual collisions depends on the size distribution of the ring particles and optical depth; if the ring were comprised entirely of 10 m grains, then the collisional timescale would be tens of millions of years, which is comparable to the inward drag timescale. Most material from 10 m to centimetres in size ultimately hits Iapetus, with smaller percentages striking Hyperion and Titan³.

References:

Verbiscer, A., Skrutskie, M., & Hamilton, D. (2009). Saturn's largest ring Nature DOI: 10.1038/nature08515

BBC article published by Jonathan Amos. 2009/10/08 (the source of the nice graphic shown above).

Spitzer press release, 2009/10/06.

Interesting Astrophysics: Sep 28 to Oct 02

2009-10-02T09:10:00.002-04:00

A mixed bag of preprints this week. From my personal perspective I'd say the Marchili et al paper on M82' SN2008iz and Acero et al's paper on a gamma ray detection of NGC 253 are the most interesting.

Galaxies and Starbursts

The radio lightcurve of SN 2008iz in M82 revealed by Urumqi observations
N. Marchili, I. Marti-Vidal, A. Brunthaler, T.P. Krichbaum, P. Mueller, X. Liu, H.-G. Song, U. Bach, R. Beswick, J.A. Zensus, arXiv:0909.5535 [ps, pdf, other]
Comments: 7 pages, 3 figures. Accepted for publication in A & A

Detection of Gamma Rays From a Starburst Galaxy
The HESS Collaboration: F. Acero, et al, arXiv:0909.4651 [ps, pdf, other]

Comments: 24 pages, 8 figures, published in Science Express, see: this http URL

Reported H.E.S.S. gamma ray detection of NGC 253, F()>220 GeV) = [5.5 +/- 1.0(stat) +/- 2.8 (sys)] times 10-13 cm-2 s-1. Much of the interpretation is done under the assumption that all the activity is due to the starburst, and NOT related to any AGN, which I'm not personally sure is a robust assumption. Still its an interesting mini-paper.

Star Formation Histories within the Antennae Galaxies (Arp 244)
Hong-Xin Zhang, Yu Gao, Xu Kong, arXiv:0909.5186 [ps, pdf, other]
Comments: 13 pages, 7 figures, accepted by MNRAS

How ubiquitous are massive starbursts in interacting galaxies?
P. Di Matteo, F. Bournaud, M. Martig, F. Combes, A.-L. Melchior, B. Semelin, arXiv:0909.5192 [ps, pdf, other]
Comments: 4 pages, Proceedings of the conference "Galaxies in isolation: exploring Nature vs Nurture" (May 2009, Granada, Spain)

Comparison of H-alpha and UV Star Formation Rates in the Local Volume: Systematic Discrepancies for Dwarf Galaxies
Janice C. Lee, Armando Gil de Paz, Christy Tremonti, Robert C. Kennicutt Jr., Samir Salim, Matthew Bothwell, Daniela Calzetti, Julianne Dalcanton, Daniel Dale, Chad Engelbracht, Jose G. Funes S.J., Benjamin Johnson, Shoko Sakai, Evan Skillman, Liese van Zee, Fabian Walter, Daniel Weisz, arXiv:0909.5205 [ps, pdf, other]
Comments: 29 pages, 10 figures, 2 tables, accepted for publication in ApJ

The Far-Infrared--Radio Correlation at High Redshifts: Physical Considerations and Prospects for the Square Kilometer Array
Eric J. Murphy, arXiv:0910.0011 [ps, pdf, other]
Comments: 16 pages, 8 figures, accepted for publication in ApJ

What stellar populations can tell us about the evolution of the mass-metallicity relation in SDSS galaxies
N. Vale Asari, G. Stasinska, R. Cid Fernandes, J. M. Gomes, M. Schlickmann, A. Mateus, W. Schoenell, arXiv:0910.0224 [ps, pdf, other]
Comments: To appear in the proceedings of IAU symposium 262, 'Stellar Populations - Planning for the Next Decade'

From their abstract: "Our results suggest that the M-Z relation for galaxies with present-day stellar masses down to 10^10 solar masses is mainly driven by the star formation history and not by inflows or outflows." This strikes me as a bit odd for a major conclusion, as pretty much everyone agrees that M-Z is dominated by the SF history... the real argument if M-yeff, and the trends suggestive of outflow really kick in for galaxies *below* 10^10.5 solar masses.

Theoretical Cosmology

Can galaxy outflows and re-accretion produce the downsizing in specific star formation rate of late-type galaxies?
C. Firmani, V. Avila-Reese, A. Rodriguez-Puebla, arXiv:0909.5188 [ps, pdf, other]
Comments: 11 pages, 4 figures. Comments are welcome. Submitted to MNRAS

The physics driving the cosmic star formation history
Joop Schaye, Claudio Dalla Vecchia, C. M. Booth, Robert P. C. Wiersma, Tom Theuns, Marcel R. Haas, Serena Bertone, Alan R. Duffy, I. G. McCarthy, Freeke van de Voort, arXiv:0909.5196 [ps, pdf, other]
Comments: Submitted to MNRAS, 27 pages and 18 figures

Numerical Astrophysics

A new radiative cooling curve based on an up to date plasma emission code
K.M. Schure, D. Kosenko, J.S. Kaastra, R. Keppens, J. Vink, arXiv:0909.5204 [ps, pdf, other]

Comments: 11 pages, 6 figures. Accepted for publication in A&A. Tables in text format online available at this http URL

Collisional ionisation equilibrium cooling, valid above 10⁴ K.. Seems pretty straightforward.

Numerical Implementation of Streaming Down the Gradient: Application to Fluid Modeling of Cosmic Rays
Prateek Sharma, Phillip Colella, Daniel F. Martin, arXiv:0909.5426 [ps, pdf, other]
Comments: submitted to SIAM J. of Scient. Comp.; 15 pages, 9 figs.; comments welcome

Stars, Supernovae and Planets

Stellar models: firm evidence, open questions and future developments
Santi Cassisi, arXiv:0909.4629 [ps, pdf, other]
Comments: 10 pages, 3 figures, Keynote review talk at the IAU Symp. 262 "Stellar Populations - Planning the Next Decade" of the XXVIIth IAU General Assembly held in Rio de Janeiro (Brazil), Proceeding eds. G. Bruzual & S. Charlot

Chandra observation of Cepheus A: The diffuse emission of HH 168 resolved
P. C. Schneider, H. M. Guenther, J. H. M. M. Schmitt, arXiv:0909.5326 [ps, pdf, other]
Comments: 8 pages, 5 figures, accepted for publication in A&A

Core collapse supernovae and starbursts
Miguel A. Perez-Torres, arXiv:0909.5578 [ps, pdf, other]
Comments: Proceedings of the 8th international e-VLBI Workshop, accepted for publication, 6 pages, 1 figure,

Brian Switek reviews the Templeton Foundation's "Test of Faith" DVD series

2009-10-01T13:56:00.001-04:00

Brian Switek has a characteristically thoughtful review of the Templeton Foundation's DVD miniseries "Test of Faith" on his blog. As Brian is not one of those evil "divisive" (or worse: "uncivil") atheists like Dawkins, Coyne or PZ Myers I'd hope that his critique is not dismissed out of hand by pro-religion accommodationists.

Unfortunately for an organization that claims to represent a serious, sober and moderate vision of (some form of) religion and science not in being in conflict, the DVDs engage in much the same sort of God-of-the-gaps teleology and straw-man argumentation that creationists normally engage in.

Nor does the Templeton Foundation's vision of religion sound particularly deist or ecumenical. Brian writes:

I would not have been so aggravated with the program if it presented scientists who said something akin to "I am a Christian/Muslim/Buddhist/Pastafarian/&c. I believe [insert belief system here] on the basis of faith, and I feel what I have come to understand about the nature of the universe is consistent with the faith I practice. Rather than make nature conform to my beliefs, however, I would rather understand the world as it is. If it turns out to be inconsistent with my faith then I will have to question what I believe." I could at least respect that. Instead the Test of Faith series trots out scientist after scientist who believe that they have some special glimmer or proof of God in nature; it is going at the whole thing backwards. The impression the series gives is that the natural world justifies and supports a particular religion, Christianity, rather than stating that some liberal forms of that religion could accept the science of evolution. (Whether evolution is reconcilable with religion depends on what brand religion we're talking about.)

And people wonder why many scientists have little or no respect for the Templeton Foundation?

PS: The 'physicist Katherine Blundell [who] says that there are "truths" in the universe that science does not detect' (*) mentioned is most probably the Oxford astronomer Katherine Blundell, as she is associated with some organization called The Faraday Institute For Science and Religion.

* Oh really. How do you know?

Interesting Astrophysics: Sep 21 to Sep 25

2009-09-25T09:41:00.002-04:00

A interesting week. Of particular note: Radio observation of young SNe/SNRs in Arp 299 (NGC 3690+IC 694) by Ulvestad and also Perez-Torres et al; empirical measures of gas consumption in galaxies by Bauermeister et al versus simulated gas accretion by Kereš et al (which makes galaxies too massive); YACRDWM (yet another cosmic ray driven wind model), this time by Samui et al; and estimates of the delay time for prompt Type Ia supernovae (Raskin et al)

Galaxies and Starbursts

Radio Emission from Young Supernovae and Supernova Remnants in Arp 299
James S. Ulvestad, arXiv:0909.3534 [ps, pdf, other]
Comments: Astronomical Journal, in press, December 2009 issue

Arp 299 = NGC 3690 + IC 694. Finds 30 point-like radio sources in the two nuclei. Also gives estimated sizes of the two regions where the young SNe/SNRs are found.

An extremely prolific supernova factory in the buried nucleus of the starburst galaxy IC 694
M.A. Perez-Torres, C. Romero-Canizales, A. Alberdi, A. Polatidis, arXiv:0909.3959 [ps, pdf, other]
Comments: Under revision by A&A, 6 pages, 2 figures

Makes a number of rather strong claims...

The Gas Consumption History to z ~ 4
Amber Bauermeister, Leo Blitz, Chung-Pei Ma, arXiv:0909.3840 [ps, pdf, other]
Comments: 10 pages, 6 figures. Submitted to ApJ

UV Continuum Slope and Dust Obscuration from z~6 to z~2: The Star Formation Rate Density at High Redshift
R.J. Bouwens, G.D. Illingworth, M. Franx, R-R. Chary, G.R. Meurer, C.J. Conselice, H. Ford, M. Giavalisco, P. van Dokkum, arXiv:0909.4074 [ps, pdf, other]
Comments: 30 pages, 15 figures, 7 tables, accepted for publication in the Astrophysical Journal

HI kinematics and dynamics of Messier 31
Laurent Chemin, Claude Carignan, Tyler Foster, arXiv:0909.3846 [ps, pdf, other]

Comments: Accepted for publication in the Astrophysical Journal, 22 pages, 17 figures. For a higher resolution version of the article, see this http URL

Low Resolution Spectral Templates For AGNs and Galaxies From 0.03 -- 30 microns
R.J. Assef, C.S. Kochanek, M. Brodwin, R. Cool, W. Forman, A.H. Gonzalez, R.C. Hickox, C. Jones, E. Le Floc'h, J. Moustakas, S.S. Murray, D. Stern, arXiv:0909.3849 [ps, pdf, other]

Comments: Submitted to The Astrophysical Journal. 23 text pages + 3 tables + 18 figures. Fortran codes, templates and electronic tables available at this http URL

Cosmic ray driven outflows from high redshift galaxies
Saumyadip Samui, Kandaswamy Subramanian, Raghunathan Srianand, arXiv:0909.3854 [pdf, other]
Comments: 14 pages, 7 figures, Submitted to MNRAS

As with all CR-driven models this relies on assuming that supernovae losing the vast majority (~90%) of their initial kinetic energy in order for the energy associated with CRs to then be significant in the remaining total. This may apply to quiescently star forming galaxies, but its a bad assumption for actively star forming galaxies.

Black Holes and AGN

Title: Characterising the Far-infrared Properties of Distant X-ray Detected AGNs: Evidence for Evolution in the Infrared--X-ray Luminosity Ratio
J. R. Mullaney, D. M. Alexander, M. Huynh, A. D. Goulding, D. Frayer, arXiv:0909.3842 [ps, pdf, other]
Comments: 20 pages, 11 figures, MNRAS accepted

Theoretical Cosmology

Galaxies in a simulated ΛCDM universe - II. Observable properties and constraints on feedback
Kereš, Dušan; Katz, Neal; Davé, Romeel; Fardal, Mark; Weinberg, David H., 2009, MNRAS, 396, 2332
Full Text: HTML, PDF (1885k)

In short they find that the over-cooling problem remains, and existing (simplistic) feedback recipes do NOT fix it.

Galaxies in a simulated ΛCDM Universe - I. Cold mode and hot cores
Kereš, Dušan; Katz, Neal; Fardal, Mark; Davé, Romeel; Weinberg, David H., 2009, MNRAS, 395, 160
Full Text: HTML, PDF (44390k)

Updated version of the older stuff on the relative strengths of cold mode and hot mode accretion onto galaxies and how accretion rates onto galaxies relate to the simulated star formation rates. NB: The end up with 3 times too many baryons in galaxies, so should we still believe that accretion is being handled correctly?

The Modelling of Feedback Processes in Cosmological Simulations of Disk Galaxy Formation
Franziska Piontek, Matthias Steinmetz, arXiv:0909.4167 [ps, pdf, other]
Comments: 21 pages, 27 figures, submitted to MNRAS

Stars, Supernovae and Planets

Discovery of Strong Radiative Recombination Continua from The Supernova Remnant IC 443 with Suzaku
Hiroya Yamaguchi, Midori Ozawa, Katsuji Koyama, Kuniaki Masai, Junko S. Hiraga, Masanobu Ozaki, Daisuke Yonetoku, arXiv:0909.3848 [ps, pdf, other]
Comments: 5 pages, 5 figures, accepted by ApJ Letter

Cosmic Origins Spectrograph Observations of the Chemical Composition of LMC N132D
Kevin France, Matthew Beasley, Brian A. Keeney, Charles W. Danforth, Cynthia S. Froning, James C. Green, arXiv:0909.4110 [ps, pdf, other]
Comments: 5 pages, 4 figures. Submitted to ApJL

Prompt Ia Supernovae Are Significantly Delayed
Cody Raskin, Evan Scannapieco, James Rhoads, Massimo Della Valle, arXiv:0909.4293 [pdf, other]
Comments: 6 pages, 6 figures, ApJ, in press

From their abstract: "Our approach confines the analysis only to the relevant portions of the hosts, allowing us to show that even so-called "prompt" SNe Ia that trace star-formation on cosmic timescales exhibit a significant delay time of 200-500 million years."

Radiation-Hydrodynamic Models of X-Ray & EUV Photoevaporating Protoplanetary Discs
J. E. Owen, B. Ercolano, C. J. Clarke, R. D. Alexander, arXiv:0909.4309 [ps, pdf, other]
Comments: 16 pages, 14 figures, accepted for publication in MNRAS

X-rays are the dominant driving mechanism for photoevaporation.

The Planetary Nebula Luminosity Function: Pieces of the Puzzle
Robin Ciardullo, arXiv:0909.4356 [ps, pdf, other]
Comments: 7 pages, including 7 figures; presentation at the workshop on the Legacies of the Macquarie/AAO/Strasbourg H-alpha Planetary Nebula project, accepted for publication in PASA

Note to self: Must read, as may have implications for understanding compact H-alpha point sources in M82 ACS data.

3D models of radiatively driven colliding winds in massive O+O star binaries - III. Thermal X-ray emission
J. M. Pittard, E. R. Parkin, arXiv:0909.4383 [ps, pdf, other]
Comments: 29 pages, 23 figures, accepted for publication in MNRAS

Other

Astroinformatics: A 21st Century Approach to Astronomy
Kirk D. Borne, arXiv:0909.3892 [pdf, other]
Comments: 14 pages total: 1 cover page, 3 pages of co-signers, plus 10 pages, Astro2010 Decadal Survey State of the Profession Position Paper

Galaxies and Cladistics
Didier Fraix-Burnet, arXiv:0909.4164 [ps, pdf, other]
Comments: Talk given at the "12th Evolutionary Biology Meeting" held in Marseille, France, Sept. 24-26, 2008
Journal-ref: Evolutionary Biology. Concept, Modeling, and Application, Pontarotti, Pierre (Ed.) (2009) 363-378

MacArthur Fellows for 2009 announced

2009-09-23T08:45:00.003-04:00

This years crop of MacArthur Fellows (the so-called genius grants) has just been announced - the list of this year's Fellows is well worth a look. I like the diversity in occupation and age they cover - its not just thirty-somethings in fashionable areas.