Tues. 11/12/12

The stellar populations of massive galaxies in the local Universe Richard M. McDermid (Submitted on 10 Nov 2012)

I present a brief review of the stellar population properties of massive galaxies, focusing on early-type galaxies in particular, with emphasis on recent results from the ATLAS3D Survey. I discuss the occurrence of young stellar ages, cold gas, and ongoing star formation in early-type galaxies, the presence of which gives important clues to the evolutionary path of these galaxies. Consideration of empirical star formation histories gives a meaningful picture of galaxy stellar population properties, and allows accurate comparison of mass estimates from populations and dynamics. This has recently provided strong evidence of a non-universal IMF, as supported by other recent evidences. Spatially-resolved studies of stellar populations are also crucial to connect distinct components within galaxies to spatial structures seen in other wavelengths or parameters. Stellar populations in the faint outer envelopes of early-type galaxies are a formidable frontier for observers, but promise to put constraints on the ratio of accreted stellar mass versus that formed ‘in situ’ – a key feature of recent galaxy formation models. Galaxy environment appears to play a key role in controlling the stellar population properties of low mass galaxies. Simulations remind us, however, that current day galaxies are the product of a complex assembly and environment history, which gives rise to the trends we see. This has strong implications for our interpretation of environmental trends.

Comments: 10 pages, 4 figures, LaTeX. Invited talk for the IAU Symposium 295 "The Intriguing Life of Massive Galaxies". To appear in Proc. of the XXVIII IAU General Assembly, Beijing, China, August 2012, eds. D. Thomas, A. Pasquali; I. Ferreras. Cambridge University Press
Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
Cite as: arXiv:1211.2317 [astro-ph.CO]
(or arXiv:1211.2317v1 [astro-ph.CO] for this version)

Unusual Carbonaceous Dust Distribution in PN G095.2+00.7 Ryou Ohsawa, Takashi Onaka, Itsuki Sakon, Tamami I. Mori, Takashi Miyata, Kentaro Asano, Mikako Matsuura, Hidehiro Kaneda (Submitted on 11 Nov 2012)

We investigate the polycyclic aromatic hydrocarbon features in the young Galactic planetary nebula PN G095.2+00.7 based on mid-infrared observations. The near- to mid-infrared spectra obtained with the AKARI/IRC and the Spitzer/IRS show the PAH features as well as the broad emission feature at 12 {\mu}m usually seen in proto-planetary nebulae (pPNe). The spatially resolved spectra obtained with Subaru/COMICS suggest that the broad emission around 12 {\mu}m is distributed in a shell-like structure, but the unidentified infrared band at 11.3 {\mu}m is selectively enhanced at the southern part of the nebula. The variation can be explained by a difference in the amount of the UV radiation to excite PAHs, and does not necessarily require the chemical processing of dust grains and PAHs. It suggests that the UV self-extinction is important to understand the mid-infrared spectral features. We propose a mechanism which accounts for the evolutionary sequence of the mid-infrared dust features seen in a transition from pPNe to PNe.

Comments: 6 pages, 4 figures
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Galaxy Astrophysics (astro-ph.GA)
Journal reference: 2012 Astrophysical Journal Letters, 760, L34
DOI: 10.1088/2041-8205/760/2/L34
Cite as: arXiv:1211.2385 [astro-ph.SR]

A New Galactic Extinction Map in High Ecliptic Latitudes Tsunehito Kohyama, Hiroshi Shibai, Misato Fukagawa, Takahiro Sumi, Yasunori Hibi (Submitted on 11 Nov 2012)

In this study, we derived a galactic extinction map in high ecliptic latitudes for |\beta| > 30 degrees. The dust temperature distribution was derived from the intensities at 100 and 140 \mu m with a spatial resolution of 5′. The intensity at 140 \mu m was derived from the intensities at 60 and 100 \mu m of the IRAS data assuming two tight correlations between the intensities at 60, 100, and 140 \mu m of the COBE/DIRBE data. We found that these correlations can be separated into two correlations by the antenna temperature of the radio continuum at 41 GHz.
Because the present study can trace the 5′-scale spatial variation in the dust temperature distribution, it has an advantage over the extinction map derived by Schlegel, Finkbeiner, and Davis, who used the DIRBE maps to derive dust temperature distribution with a spatial resolution of 1 degrees. We estimated the accuracy of our method by comparing it with that of Schlegel, Finkbeiner, and Davis. The spatial resolution difference was found to be significant. The area in which the significant difference is confirmed occupies 28% of the region for |\beta| > 30 degrees.
With respect to the estimation of extragalactic reddening, the present study has an advantage over the extinction map derived by Dobashi (2011), which was based on the 2MASS Point Source Catalog, because our extinction map is derived on the basis of far-infrared emission. Dobashi’s extinction map exhibits a maximum value that is lower than that of our map in the galactic plane and a signal-to-noise ratio that is lower than that of our map in high galactic latitudes. This significant difference is confirmed in 81% of the region for |\beta| > 30 degrees.
In the areas where the significant differences are confirmed, the extinction should be estimated using our method rather than the previous methods.

Comments: 28 pages, 14 figures, accepted for publication in PASJ
Subjects: Galaxy Astrophysics (astro-ph.GA)
Cite as: arXiv:1211.2382 [astro-ph.GA]
(or arXiv:1211.2382v1 [astro-ph.GA] for this version)
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