Astro Seminar: "The Relationship Between Quasar Activity and Diffuse Cool Halo Gas -- Feeding or Feedback?"

Wed, 02/15/2017 - 14:00
Sean Johnson (Princeton/Carnegie)

The growth and evolution of galaxies is fueled by gas accretion from circum-/intergalactic gas reservoirs. In turn, gas accretion and cooling is regulated by outflows and heating from supernovae and active galactic nuclei. These outflows enrich the intergalactic medium with heavy elements and produce massive baryon reservoirs in the form of diffuse halo gas. Consequently, the diffuse gas of the inter- and circum-galactic medium (IGM/CGM) represent a sensitive laboratory for studying the accretion and feedback processes that regulate galaxy evolution. Except under extreme conditions however, the gas of the IGM/CGM is too diffuse to observe in emission with current facilities, but it can be observed in absorption when UV bright background sources are serendipitously behind a foreground galaxy halo. I will present results from a survey of the cool halo gas content in quasar host halos at z~1 on 30-300 kpc scales using a serendipitous sample of 200 foreground-background quasar pairs from the SDSS. This sample reveals an unexpected relationship between quasar activity and cool halo gas in the form of a correlation between absorbing gas at <~200 kpc and quasar luminosity as well as extreme gas kinematics not seen for non-AGN galaxies. These observations provide tantalising hints at the large-scale impact of quasar feedback and complex nature of quasar feeding that can be explored further with on-going observations.

David Rittenhouse Laboratory, A4