Friday Feb. 8

Unveiling The Sigma-Discrepancy II: Revisiting the Evolution of ULIRGs & The Origin of Quasars

Barry Rothberg (1,2,3,4), Jacqueline Fischer (5), Myriam Rodrigues (6), David B. Sanders (7) ((1) National Research Council Postdoctoral Fellow at Naval Research Laboratory, (2) Space Telescope Science Institute, (3) George Mason University, Department of Physics & Astronomy, (4) Leibniz-Institut fur Astrophysik Potsdam (AIP), (5) Naval Research Laboratory, (6) European Southern Observatory, (7) Institute for Astronomy, University of Hawaii)
(Submitted on 7 Feb 2013)

We present the first central velocity dispersions (sigma_o) measured from the 0.85 micron Calcium II Triplet (CaT) for 8 advanced (i.e. single nuclei) local (z < 0.15) Ultraluminous Infrared Galaxies (ULIRGs). First, these measurements are used to test the prediction that the "sigma-Discrepancy," in which the CaT sigma_o is systematically larger than the sigma_o obtained from the 1.6 or 2.3 micron stellar CO band-heads, extends to ULIRG luminosities. Next, we combine the CaT data with rest-frame I-band photometry obtained from archival Hubble Space Telescope data and the Sloan Digital Sky Survey (SDSS) to derive dynamical properties for the 8 ULIRGs. These are then compared to the dynamical properties of 9,255 elliptical galaxies from the SDSS within the same redshift volume and of a relatively nearby (z < 0.4) sample of 53 QSO host galaxies. A comparison is also made between the I-band and H-band dynamical properties of the ULIRGs. We find four key results: 1) the sigma-Discrepancy extends to ULIRG luminosities; 2) at I-band ULIRGs lie on the Fundamental Plane (FP) in a region consistent with the most massive elliptical galaxies and not low-intermediate mass ellipticals as previously reported in the near-infrared; 3) the I-band M/L of ULIRGs are consistent with an old stellar population, while at H-band ULIRGs appear significantly younger and less massive; and 4) we derive an I-band Kormendy Relation from the SDSS ellipticals and demonstrate that ULIRGs and QSO host galaxies are dynamically similar.

Comments: Accepted to The Astrophysical Journal. 6 Figures, 5 Tables, 4 Appendices
Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
Cite as: arXiv:1302.1680 [astro-ph.CO]
(or arXiv:1302.1680v1 [astro-ph.CO] for this version)

Testing 24 micron and Infrared Luminosity as Star Formation Tracers for Galactic Star Forming Regions

Nalin Vutisalchavakul, Neal J. Evans II
(Submitted on 7 Feb 2013)

We have tested some relations for star formation rates used in extra-galactic studies for regions within the Galaxy. In nearby molecular clouds, where the IMF is not fully-sampled, the dust emission at 24 micron greatly underestimates star formation rates (by a factor of 100 on average) when compared to star formation rates determined from counting YSOs. The total infrared emission does no better. In contrast, the total far-infrared method agrees within a factor of 2 on average with star formation rates based on radio continuum emission for massive, dense clumps that are forming enough massive stars to have the total infrared luminosity exceed 10^4.5 Lsun. The total infrared and 24 micron also agree well with each other for both nearby, low-mass star forming regions and the massive, dense clumps regions.

Subjects: Galaxy Astrophysics (astro-ph.GA)
Cite as: arXiv:1302.1858 [astro-ph.GA]
(or arXiv:1302.1858v1 [astro-ph.GA] for this version)
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