14 March 2002 CfA Colloquium


Title: Molecular Gas and the Host Galaxies of Infrared Excess Quasi-Stellar Objects

Speaker: Aaron Evans

Abstract:

Quasi-stellar Objects (QSOs) and Ultraluminous Infrared Galaxies (ULIGs) make up the bright end of the local luminosity function. A significant amount of work has been done over the last 15 years characterizing the stellar populations, the dynamical state of the host galaxies, and the dominant sources of atomic gas ionization in both ULIGs and QSOs; these studies have attempted to establish whether or not ULIG and QSOs are two phases of an evolutionary sequence of massive galaxy mergers. In order to establish the presence of fuel for both star formation and active galactic nuclear activity, a molecular gas survey of z < 0.2 optically selected QSOs has been initiated. This sample of QSOs have infrared-excesses (L_IR [8-1000um] / L [0.1-1um]) > 0.36, making them likely transition sources between the ULIG and UV-excess QSO phenomena. I will compare the millimeter data and recently obtained optical and near-infrared imaging observations of this IR-excess sample with that of local ULIGs and discuss these in the context of the dust enshrouded-quasar model of ULIGs.

References for students:

Ultraluminous Infrared Galaxies and the Origin of Quasars D. B. Sanders, B. T. Soifer, J. H. Elias, B. F. Madore, K. Matthews, G. Neugebauer, & N. Z. Scoville 1988, ApJ, 325, 74

Molecular Gas in Infrared-Excess, Optically-Selected QSOs and the Connection with Infrared Luminous Galaxies Evans, A. S., Frayer, D. T., Surace, J. A., & Sanders, D. B. 2001, AJ, 121, 3286

Optical/Near-Infrared Imaging of Infrared-Excess Palomar-Green QSOs Surace, J. A., Sanders, D. B., & Evans, A. S. 2001, AJ, 122, 2791