Friday, January 02, 2009

Interesting Astrophysics: Dec 29 - Jan 02

The final edition of Interesting Astrophysics for 2008, and first edition of 2009. There really isn't much this week in terms of numbers, largely thanks to their only being one release of preprints on arXiv.org and the email notifications from the main peer-reviewed journals don't seem to functioning this week.

Nevertheless, I firmly believe that one good starburst paper is worth a thousand normal papers, and this week its not just any starburst but the archetype M82 itself.


Galaxies and Starbursts

Near-IR spectroscopic ages of massive star clusters in M82
A. Lançon, J. S. Gallagher III, M. Mouhcine, L. J. Smith, D. Ladjal, R. de Grijs, arXiv:0812.4888 [ps, pdf, other]
Comments: 14 pages, 20 figures, uses aa.cls
Journal-ref: Astronomy and Astrophysics, 486, 165 (2008)

NIR ages between 9 - 30 Myr. This is somewhat older than typically optically-derived ages of the brighter clusters in M82. Its certainly very plausible that active star formation within the center of M82 has been going on for more than 10 Myr, but thats not quite the point that this paper is making. That optical and NIR-derived ages can differ for the same clusters... that is something people need to keep in mind when modeling the starburst (is this apparent age discrepency due to the lack of binaries in stellar population synthesis models?).

Frankly I worry about how accurate estimates of the starburst age are for even well-studied starbursts like M82 and NGC 1569. Are there any truly young starbursts (as the Wolf rayet galaxies were widely assumed to be a decade or so ago), with no significant burst star formation older than a few Myr? Are there any truly post-starburst objects with no significant star formation within the last 10-20 Myr (as NGC 1569 is widely claimed to be)?

Biases and Uncertainties in Physical Parameter Estimates of Lyman Break Galaxies from Broad-band Photometry
Seong-Kook Lee, Rafal Idzi, Henry C. Ferguson, Rachel S. Somerville, Tommy Wiklind, Mauro Giavalisco, arXiv:0812.5111 [ps, pdf, other]
Comments: 85 pages, 34 figures, submittted to ApJS

Ultraviolet Spectra of Local Galaxies and their Link with the High-z Population
Claus Leitherer, arXiv:0812.5113 [pdf]
Comments: 8 pages, invited talk given at the conference "Probing Stellar Populations out to the Distant Universe", Cefalu (Italy), September 7 - 19, 2008. To be published in the AIP Conf. Proc. Series


Cosmology

Dissecting Pamela (and ATIC) with Occam's Razor: existing, well-known Pulsars naturally account for the "anomalous" Cosmic-Ray Electron and Positron Data
Stefano Profumo, arXiv:0812.4457 [ps, pdf, other]
Comments: 23 pages, 14 figures, submitted to Phys.Rev.D

Maybe this should be filed under Compact Objects, but as it deals with the PAMELA and ATIC data previously interpreted as a possible Dark Matter annihilation signal it seems fitting to class this paper as Cosmology.

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