Friday, January 09, 2009

Interesting astrophysics: Jan 05 - Jan 09

With the new year finally underway and all the annoying holidays over there is more in the way of interesting peer-reviewed and preprint astrophysics available this week. To make my comments more clearly separable from the preprints/papers I'm going to switch to using italic for any personal comments below the dividing line below.

There has also been some interesting galaxy and galaxy formation stuff coming out the this week's American Astronomical Society meeting in Long Beach (I didn't go, as I consider AAS meetings overly expensive drains of grant money given that you get less detailed science out of them) at least in press release form (and with press release hype too, in one case). If time permits I'll cover those separately.

Galaxies and Starbursts

New knowledge of the Galactic magnetic fields
J.L. Han, arXiv:0901.0040 [ps, pdf, other]
Comments: 8 pages, 4 figures. Invited Talk at XIV International Symposium on Very High Energy Cosmic Ray Interactions, WeiHai, China 15-22 Aug 2006
Journal-ref: Nuclear Physics B Proc. Suppl 175, 62 (2008)

Interplay of CR-driven galactic wind, magnetic field, and galactic dynamo in spiral galaxies
Marita Krause, arXiv:0901.0845 [ps, pdf, other]
Comments: 2 pages. To be published in "Cosmic Magnetic Fields: From Planets, to Stars and Galaxies", K.G. Strassmeier, A.G. Kosovichev & J.E. Beckman, eds., Proc. IAU Symp. 259, CUP

This seems to be the most interesting part of the Krause preprint, at least with respect to galactic winds:
"For NGC 253 Heesen et al. (this volume) argued that the synchrotron lifetime (which is / B_{t}^{−2}) mainly determines the vertical scale height of the synchrotron emission and estimated the cosmic ray bulk velocity to 300±30 km/s. As this is similar to the escape velocity, it shows the presence of a galactic wind in this galaxy. The fact that we observe similar averaged scaleheights at lambda = 6 cm for the four galaxies mentioned above imply that the galactic wind velocity is proportional to B^{+2}_{t}, and hence proportional to SFR^{0.7±0.3}."
Their are a number of differences between their interpretation and non-radio-based studies of galactic winds. Firstly, their argument is that the scale height of the radio emission is related the lifetime (and hence velocity) of the synchrotron emitting CR population, and implicitly that v_{CR} is equivalent to the wind velocity. This is very different to our interpretation of what sets the apparent 1 to 4 kpc scale height of the X-ray-emitting halos in starbursts, which was that it was the scale-height of the pre-existing halo made visible through the collision between the outflowing wind and the halo. Secondly, optically-measured velocities (using the NaD doublet in absorption) in superwinds (again, NOT NECESSARILY THE SAME AS THE TRUE WIND VELOCITY), appear to show v_{opt} proportional to SFR^{1/3} at low and moderate SFR before peaking at or below 1000 km/s at high SFR (ULIRG class galaxies), see e.g. Martin (2005). Admittedly these optical results have a lot of scatter and uncertainty, and the trends are partially driven by low number statistics at the low SFR end, but we did find the same general trend using UV-absorption lines in Grimes et al (in press). Anyway, their work is interesting, even if I doubt buy the interpretation.

Imaging the Circumnuclear Region of NGC 1365 with Chandra
Junfeng Wang, G. Fabbiano, M. Elvis, G. Risaliti, J. M. Mazzarella, J. H. Howell, S. Lord, arXiv:0901.0297 [ps, pdf, other]
Comments: Accepted for publication in The Astrophysical Journal (April 2009). 50 pages, 13 figures, 6 tables

Star Formation Around Supergiant Shells in the LMC
Laura G. Book, You-Hua Chu, Robert A. Gruendl, Yasuo Fukui, arXiv:0901.0400 [ps, pdf, other]
Comments: 12 pages, 4 figures, accepted for publication in the Astronomical Journal, improved image quality of figures

Ionization of Infalling Gas
L. M. Haffner, A. K. Duncan, S. M. Hoffman, G. J. Madsen, A. S. Hill, R. J. Reynolds, arXiv:0901.0940 [ps, pdf, other]
Comments: 4 pages, 2 figures; to appear in proceedings of "The Role of Disk-Halo Interaction in Galaxy Evolution: Outflow vs Infall?" held in Espinho, Portugal during 2008 August

The warm ionized medium in spiral galaxies
L. M. Haffner, R.-J. Dettmar, J. E. Beckman, K. Wood, J. D. Slavin, C. Giammanco, G. J. Madsen, A. Zurita, R. J. Reynolds, arXiv:0901.0941 [pdf, other]
Comments: 29 pages, 19 figures; accepted by Reviews of Modern Physics

The mass-metallicity gradient relation of early-type galaxies
Max Spolaor, Robert N. Proctor, Duncan A. Forbes, Warrick J. Couch, arXiv:0901.0548 [ps, pdf, other]
Comments: 5 pageg, 3 figures, accepted by ApJ Letter

The flat oxygen abundance gradient in the extended disk of M83
Fabio Bresolin, Emma Ryan-Weber, Robert C. Kennicutt, Quinton Goddard, arXiv:0901.1127 [ps, pdf, other]
Comments: 17 pages, 9 figures, accepted for publication in The Astrophysical Journal

Black Holes and AGN

Radiation pressure and absorption in AGN: results from a complete unbiased sample from Swift
A.C. Fabian, R. V. Vasudevan, R. F. Mushotzky, L. M. Winter, C.S. Reynolds, arXiv:0901.0250 [ps, pdf, other]
Comments: 4 pages, 2 figures, MNRAS in press

The evolution of star formation in quasar host galaxies
Stephen Serjeant, Evanthia Hatziminaoglou, arXiv:0901.0552 [ps, pdf, other]
Comments: MNRAS, accepted on 22 Dec 2008. Uses BoxedEPS (included)

Near-Infrared Spectroscopy of Seyfert Galaxies. Nuclear Activity and Stellar Population
Cristina Ramos Almeida, Ana Maria Perez Garcia, Jose Antonio Acosta Pulido, arXiv:0901.0999 [ps, pdf, other]
Comments: 44 pages, 16 figures. Accepted for publication in ApJ


Modeling and Reproducibility of Suzaku HXD PIN/GSO Background
Yasushi Fukazawa, Tsunefumi Mizuno, Shin Watanabe, Motohide Kokubun, Hiromitsu Takahashi, Naomi Kawano, Sho Nishino, Mahito Sasada, Hirohisa Shirai, Takuya Takahashi, Tomonori Yamasaki, Tomonori Yasuda, Aya Bamba, Masanori Ohno, Tadayuki Takahashi, Masayoshi Ushio, Teruaki Enoto, Takao Kitaguchi, Kazuo Makishima, Kazuhiro Nakazawa, Yuichi Uehara, Shin'ya Yamada, Takayuki Yuasa, Naoki Isobe, Madoka Kawaharada, Takaaki Tanaka, Makoto Tashiro, Yukikatsu Terada, Kazutaka Yamaoka, arXiv:0901.0419 [ps, pdf, other]
Comments: 29 pages, 45 figures, will appear on the PASJ 61, Suzaku 3rd issue

Numerical Astrophysics and Hydrodynamics

Turbulence and Magnetic Field Amplification in Supernova Remnants: Interactions Between A Strong Shock Wave and Multi-Phase Interstellar Medium
Tsuyoshi Inoue, Ryo Yamazaki, Shu-ichiro Inutsuka, arXiv:0901.0486 [ps, pdf, other]
Comments: 10 pages, 10 figures, submitted to ApJ

Stars, Star Clusters and Supernovae

An Infrared Census of Star Formation in the Horsehead Nebula
Brendan P. Bowler, William H. Waller, S. Thomas Megeath, Brian M. Patten, Motohide Tamura, arXiv:0901.0564 [ps, pdf, other]
Comments: 30 pages, 11 figures; accepted for publication in The Astronomical Journal

The Formation Rates of Population III Stars and Chemical Enrichment of Halos during the Reionization Era
M. Trenti, M. Stiavelli, arXiv:0901.0711 [ps, pdf, other]
Comments: 31 pages, 8 figures, ApJ accepted

3D modelling of the colliding winds in Eta Carinae - evidence for radiative inhibition
E. R. Parkin, J. M. Pittard, M. F. Corcoran, K. Hamaguchi, I. R. Stevens, arXiv:0901.0862 [ps, pdf, other]
Comments: 20 pages, 24 Figures, accepted to MNRAS


The distribution of stellar mass in the low-redshift Universe
Cheng Li, Simon D. M. White, arXiv:0901.0706 [ps, pdf, other]
Comments: 10 pages, 7 figures, submitted for publication in Monthly Notices

Tracing the Reionization-Epoch Intergalactic Medium with Metal Absorption Lines
Benjamin D. Oppenheimer, Romeel Davé, Kristian Finlator, arXiv:0901.0286 [ps, pdf, other]
Comments: Submitted to MNRAS, 28 pages, 19 figures

Personally I think the way they implement galactic winds as heavily mass-loaded single phase flows is simply not justified (or actually counter-indicated) by existing observational data and theoretical modeling of local starburst-driven winds. With a non-physical representation of superwinds, any wind-related results obtained in this manner can not be considered robust (they might be mildly wrong or badly wrong, and without doing it the right way its hard to know how meaningful the results are). The authors would probably argue in their defense that their method reproduces certain observational galaxy or wind-related requirements and hence is reasonable/accurate/"observationally calibrated". My response is that I dispute the robustness and applicability of those observational requirements as constraints on wind models, especially winds in the numerical form incorporated in cosmological models.

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