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Abstracts (9/28) Accretion Disk Temperatures and Continuum Colors in QSOs Accretion disk temperatures in QSOs can be estimated from the QSO luminosity and the mass of the central black hole. Observed colors of SDSS QSOs generally do not show the expected trend of bluer colors for hotter disks. (10/19) The Dynamical Evolution of Galaxies in Compact Groups: Insights from VLA HI and Spitzer mid-IR Studies Hickson Compact Groups of galaxies provide a unique environment to study the mechanisms by which star formation occurs amid continuous gravitational encounters. These dense groups host a variety of star formation modes, and they can provide insight into the role of gas in galaxy evolution. I will present new Spitzer IRAC (3- 8.0 microns) and MIPS (24 micron) observations in combination with HI observations to examine star formation and HI gas content in a sample of HCGs. I will discuss how the infrared spectral energy distributions are used to evaluate the level of star formation activity. I will also discuss how the HI morphology and gas kinematics may be interpreted as multiple stages of group evolution. (11/9) Journal Club: FeII and MgII in Luminous, Intermediate- Redshift, Narrow-Line Seyfert 1 Galaxies from the Sloan Digital Sky Survey We present results from analysis of spectra from a sample of ~900 quasars from the Sloan Digital Sky Survey. These objects were selected for their intermediate redshift (1.2<z<1.8), placing Mg II and UV Fe II in the optical bandpass, relatively narrow Mg II lines, and moderately good signal-to-noise ratio spectra. Using a maximum likelihood analysis, we discovered that there is a significant dispersion in the Fe II/Mg II ratios in the sample. Using simulations, we demonstrate that this range and the corresponding correlation between Fe II equivalent width and Fe II/ Mg II ratio are primarily a consequence of a larger dispersion of Fe II equivalent width (EW) relative to Mg II EW. This larger dispersion in Fe II EW could be a consequence of a range in iron abundance or a range of Fe II excitation. The latter possibility is supported by evidence that objects with weak (zero) C II] λ2325 equivalent width are likely to have large Fe II/Mg II ratios. We discuss physical effects that could produce a range of Fe II/Mg II ratios. |
2 November 2006
Astronomy Program · The University of Texas at Austin · Austin, Texas 78712
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Astronomy Program · The University of Texas at Austin · Austin, Texas 78712
prospective student inquiries: studentinfo@astro.as.utexas.edu
site comments: www@www.as.utexas.edu