Interesting Astrophysics: Sep 07 to Sep 11

Of particular note there are interesting papers on theoretical models of dust-driven stellar winds (Mattsson et al) and SN Ia-driven galactic winds (Tang et al), along with observations of z~3 star forming galaxies showing signs of superwinds driven by core collapse supernova activity (Lemoine-Busserolle et al).

I also found Guio & Achilleos's paper on image decomposition using Voronoi tessellation quite interesting.

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Galaxies and Starbursts

Cosmic-ray driven dynamo in the interstellar medium of irregular galaxies
H. Siejkowski, M. Soida, K. Otmianowska-Mazur, M. Hanasz, D.J. Bomans, arXiv:0909.0926 [ps, pdf, other]
Comments: 8 pages, 6 figures, submitted to A&A

The Distribution of Stars and Stellar Remnants at the Galactic Center
David Merritt, arXiv:0909.1318 [ps, pdf, other]
Comments: 22 pages, 18 figures

2D Kinematics and Physical Properties of z~3 Star-Forming Galaxies
M. Lemoine-Busserolle, A. Bunker, F. Lamareille, M. Kissler-Patig, arXiv:0909.1386 [pdf, other]
Comments: 14 pages and 16 figures

Their UV spectra show ISM lines blue shifted with respect to [O III]. Galactic winds! Although of course I shouldn't be surprised.

MMTF-Halpha and HST-FUV Imaging of the Filamentary Complex in Abell 1795
Michael McDonald, Sylvain Veilleux, arXiv:0909.1554 [ps, pdf, other]
Comments: Accepted for publication in ApJ Letters, 6 pages, 4 figures, 1 table

Investigating the far-IR/radio correlation of star-forming Galaxies to z= 3
N. Seymour, M. Huynh, T. Dwelly, M. Symeonidis, A. Hopkins, I. M. McHardy, M. J. Page, G. Rieke, 2009, MNRAS, 398, 1573
Full Text: HTML, PDF (Size: 751K)

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Numerical Astrophysics & Hydrodynamics

Storm fronts over galaxy discs: models of how waves generate extraplanar gas and its anomalous kinematics
Curtis Struck and Daniel C. Smith, 2009, MNRAS, 398, 1069
Full Text: HTML, PDF (Size: 23343K)

The VOISE algorithm: a versatile tool for automatic segmentation of astronomical images
P. Guio and N. Achilleos, 2009, MNRAS, 398, 1254
Full Text: HTML, PDF (Size: 1354K)

Type Ia supernova-driven Galactic bulge wind
Shikui Tang, Q. Daniel Wang, Mordecai-Mark Mac Low, M. Ryan Joung, 2009, MNRAS, 398, 1468
Full Text: HTML, PDF (Size: 18550K)

The fragmentation of expanding shells – I. Limitations of the thin-shell approximation
James E. Dale, Richard Wünsch, Anthony Whitworth, Jan Palouš, 2009, MNRAS, 398, 1537
Full Text: HTML, PDF (Size: 16967K)

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Stars, Supernovae and Planets

The relation between the most-massive star and its parental star cluster mass
C. Weidner, P. Kroupa, I. Bonnell, arXiv:0909.1555 [ps, pdf, other]
Comments: 26 pages, 13 figures, 3 tables, accepted for publication in MNRAS

Dust Driven Mass Loss from Carbon Stars as Function of Stellar Parameters - I. A Grid of Solar-metallicity Wind Models
Lars Mattsson, Rurik Wahlin, Susanne Hoefner, arXiv:0909.1513 [ps, pdf, other]
Comments: 27 pages, 11 figures, accepted for publication in Astronomy & Astrophysics

Interesting Astrophysics: Jun 01 - Jun 05

A mixed bag this week. Of particular note are the two papers on the ever-interesting M82, a paper on Lyα-driven supershell acceleration, problems with the clumpfind algorithm, and a paper discussing the historical perception of astronomers within society.

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Galaxies and Starbursts

M82 as a Galaxy: Morphology and Stellar Content of the Disk and Halo
Y. Divakara Mayya, Luis Carrasco, arXiv:0906.0757 [ps, pdf, other]
Comments: 12 pages, To appear in the proceedings of "A Long Walk Through Astronomy: A Celebration of Luis Carrasco's 60th Birthday", Huatulco, Mexico, October 2008, ed. E. Recillas, L. Aguilar, A. Luna, and J.R. Valdes; RevMexAA (Serie de Conferencias)

Age and Extinction of the Ultraviolet Emitting Regions in M82
L.H. Rodriguez-Merino, D. Rosa-Gonzalez, Y.D. Mayya, L. Carrasco, A. Luna, R. Romano, arXiv:0906.0759 [ps, pdf, other]
Comments: 6 pages, To appear in the proceedings of "A Long Walk Through Astronomy: A Celebration of Luis Carrasco's 60th Birthday", Huatulco, Mexico, October 2008, ed. E. Recillas, L. Aguilar, A. Luna, and J.R. Valdes; RevMexAA (Serie de Conferencias)

Strong PAH Emission from z~2 ULIRGs
Vandana Desai, B. T. Soifer, Arjun Dey, Emeric Le Floc'h, Lee Armus, Kate Brand, Michael J. I. Brown, Mark Brodwin, Buell T. Jannuzi, James R. Houck, Daniel W. Weedman, Matthew L. N. Ashby, Anthony Gonzalez, Jiasheng Huang, Howard A. Smith, Harry Teplitz, Steve P. Willner, Jason Melbourne, arXiv:0905.4274 [ps, pdf, other]
Comments: accepted for publication in ApJ

Starburst and cirrus models for submillimeter galaxies
Andreas Efstathiou, Ralf Siebenmorgen, arXiv:0906.0446 [ps, pdf, other]
Comments: 9 pages, AA accepted

Redistributing hot gas around galaxies: do cool clouds signal a solution to the overcooling problem?
Tobias Kaufmann, James S. Bullock, Ariyeh H. Maller, Taotao Fang and James Wadsley, 2009, MNRAS, 396, 191
Full Text: HTML, PDF (Size: 20923K)

Acceleration of galactic supershells by Lyα radiation
Mark Dijkstra and Abraham Loeb, 2009, MNRAS, 396, 377
Full Text: HTML, PDF (Size: 608K)

The Star Formation Rate in the Reionization Era as Indicated by Gamma-ray Bursts
Matthew D. Kistler, Hasan Yuksel, John F. Beacom, Andrew M. Hopkins, J. Stuart B. Wyithe, arXiv:0906.0590 [ps, pdf, other]
Comments: 4 pages, 4 figures

The Evolution of Gas Clouds Falling in the Magnetized Galactic Halo: High Velocity Clouds (HVCs) Originated in the Galactic Fountain
Kyujin Kwak, Robin L. Shelton, Elizabeth A. Raley, arXiv:0906.0613 [ps, pdf, other]
Comments: 46 pages, 16 figures, 3 tables. Accepted for publication in ApJ

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AGN and Black Holes

Self-Regulation of AGN in Galaxy Clusters
M. Brueggen, E. Scannapieco, arXiv:0905.4726 [ps, pdf, other]
Comments: accepted by MNRAS

Towards a Complete Census of AGNs in Nearby Galaxies: A Large Population of Optically Unidentified AGNs
Andy Goulding, Dave Alexander, arXiv:0906.0772 [ps, pdf, other]
Comments: 33 pages, 11 figures, accepted for publication in MNRAS

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X-ray Astronomy

Non-Maxwellian electron distributions in clusters of galaxies
J.S. Kaastra, A.M. Bykov, N. Werner, arXiv:0905.4802 [ps, pdf, other]
Comments: 6 pages, 4 figures, accepted for publication in Astronomy and Astrophysics, main journal

The MAXI Mission on the ISS: Science and Instruments for Monitoring All Sky X-Ray Images
Masaru Matsuoka, et al, arXiv:0906.0631 [ps, pdf, other]
Comments: 12 pages, 11 figures, accepted for publication in Publications of the Astronomical Society of Japan

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Other

Resolving mixing in Smoothed Particle Hydrodynamics
J. I. Read, T. Hayfield, O. Agertz, arXiv:0906.0774 [ps, pdf, other]

Comments: Submitted to MNRAS. An OSPH patch for GADGET-2, some movies, our full multiphase test suite, and a high resolution version of the paper are all available for download from the Astro-Code wiki: this http URL

The Perils of Clumpfind: The Mass Spectrum of Sub-structures in Molecular Clouds
Jaime E. Pineda, Erik W. Rosolowsky, Alyssa A. Goodman, arXiv:0906.0331 [ps, pdf, other]
Comments: 5 pages, 3 figures. Accepted for publication in ApJ Letters

Full abstract: "We study the mass spectrum of sub-structures in the Perseus Molecular Cloud Complex traced by 13CO (1-0), finding that $dN/dM\propto M^{-2.4}$ for the standard Clumpfind parameters. This result does not agree with the classical $dN/dM\propto M^{-1.6}$. To understand this discrepancy we study the robustness of the mass spectrum derived using the Clumpfind algorithm. Both 2D and 3D Clumpfind versions are tested, using 850 $\mu$m dust emission and 13CO spectral-line observations of Perseus, respectively. The effect of varying threshold is not important, but varying stepsize produces a different effect for 2D and 3D cases. In the 2D case, where emission is relatively isolated (associated with only the densest peaks in the cloud), the mass spectrum variability is negligible compared to the mass function fit uncertainties. In the 3D case, however, where the 13CO emission traces the bulk of the molecular cloud, the number of clumps and the derived mass spectrum are highly correlated with the stepsize used. The distinction between "2D" and "3D" here is more importantly also a distinction between "sparse" and "crowded" emission. In any "crowded" case, Clumpfind should not be used blindly to derive mass functions. Clumpfind's output in the "crowded" case can still offer a statistical description of emission useful in inter-comparisons, but the clump-list should not be treated as a robust region decomposition suitable to generate a physically-meaningful mass function. We conclude that the 13CO mass spectrum depends on the observations resolution, due to the hierarchical structure of MC. "

Statistical techniques in cosmology
Alan Heavens, arXiv:0906.0664 [pdf, other]
Comments: Lectures given at the 'Francesco Lucchin' summer school, Bertinoro, Italy, May 2009, Director G. Zamorani

Public Perception of Astronomers: Revered, Reviled and Ridiculed
Michael J. West, arXiv:0905.3956 [pdf, other]
Comments: Invited review to appear in The Role of Astronomy in Society and Culture: Proceedings of IAU Symposium No. 260, 2009. D. Valls-Gabaud and A. Boksenberg, eds; typos corrected in revised version

V. Interesting.

Component analysis, causal inference, and general intelligence

The aim of astronomy is astrophysics - we observe to Universe with the hope of using the resulting data to understand the fundamental physical processes that give rise to its observed properties.

As with many sciences the data obtained from observation (experimentation, in other sciences) itself does not uniquely tell you the physics or what caused what. Instead one normally investigates to look for correlations between different aspects of the data.

For example it is known that the surface brightness, effective radius and velocity dispersion of the stars in elliptical galaxies are strongly correlated, a result now called the fundamental plane. Another example is that in starburst galaxies the soft X-ray luminosity is linearly proportional to the galaxies far-IR luminosity because, causually, the FIR traces the formation rate of massive stars, the same stars that very rapidly die and whose supernovae heat the ISM to X-ray-emitting temperatures.

Various methods of investigating correlations between multiple variables exist (e.g. principal component analysis), now often referred to as "data mining." The problem is that these methods, while useful at recasting the data in ways that aid visualization of any correlations in the data variables, do not necessarily tell you what caused what.

An interesting discussion of these often-forgotten issues and complexities, one is applicable even to astrophysics, can be found in Cosma Shalizi's article on the myth of g, the so-called general factor of intelligence. Indeed, he argues that while factor analysis is perfectly valid for data exploration or model testing, as a method for finding causal structure it is not reliable (it can be right, but often its completely wrong and can fool you).

All very interesting, and rather important to understand in the wake of a certain elderly Nobel-prize winner's recent counter-factual comments.