NAS's Astro2010 Decacal Survey recommendations

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

Interesting Astrophysics: June 01 to June 11

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.

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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."

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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."

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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.

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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."

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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

Interesting Astrophysics: 17 May to 28 May

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

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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?

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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&amp;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

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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

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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)

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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."

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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&amp;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?

Interesting Astrophysics: Mar 23 to Mar 31

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.

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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

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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. "

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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

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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.

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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 &amp; 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: 22 Feb to 05 Mar, 2010

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.

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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."

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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"

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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.

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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!

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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."

Interesting Astrophysics: Jan 18 to Jan 29

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.

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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."

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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)

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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

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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

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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).

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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."