AAS 205th Meeting, 9-13 January 2005
Session 167 Quasars and Blazars
Oral, Thursday, January 13, 2005, 2:00-3:30pm, Royal Palm 1-3

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[167.01] Ancient Starbursts in Classical QSO Host Galaxies

G. Canalizo (UC Riverside, IGPP), A. Stockton (IfA, U Hawaii)

Recent HST and ground-based studies appear to indicate that essentially all QSO host galaxies are strongly dominated by normal and apparently old bulges. To investigate the stellar populations of these objects further, we have conducted a deep Keck LRIS spectroscopic survey of the host galaxies of a sample of 16 z~0.2 classical QSO host galaxies that are seemingly normal, quiescent elliptical galaxies. Modeling of the stellar populations indicates that there are traces of major starburst episodes (involving >10% of the mass of the stellar component) in ~2/3 of the hosts, with ages ranging from 0.6 Gyr to 1.6 Gyr. While there are uncertainties in the precise starburst age estimates due to metallicity, initial mass function, and the models themselves, the high S/N ratio Keck spectra clearly show a stellar component that is significantly older than a few x108 yr and that cannot be mimicked either by a small amount of constant star formation or by one or more less dramatic, younger starburst phases. We discuss the possibility that these starbursts may be linked to past merger events that triggered both the star formation and the nuclear activity.

The author(s) of this abstract have provided an email address for comments about the abstract: gabriela.canalizo@ucr.edu

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© 2004. The American Astronomical Society.