Saturday, January 30, 2010

Geoffrey Burbidge passes away (Jan 26 2010)

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.]

Friday, January 29, 2010

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.

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]
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."

Thursday, January 21, 2010

Soft money

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).

Friday, January 15, 2010

Interesting Astrophysics: 01 Jan to 15 Jan, 2010

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 &amp; 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.


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!