Speaker: Kate Rubin, Harvard-Smithsonian Center for Astrophysics
Abstract: The environments extending several hundred kiloparsecs from galaxies contain the fuel that feeds galactic star formation, and act as the reservoir into which ejecta from stellar and AGN feedback are driven. Observations of the cool hydrogen and metal content of these regions (i.e., the circumgalactic medium, or CGM) can therefore provide incisive tests of our understanding of these processes. I will briefly discuss current constraints on the content of the CGM around massive, > L* galaxies from z~2 to ~0. I will then describe a new technique that pinpoints much fainter, sub-luminous systems at z~2, allowing us to probe the gas in their surroundings in absorption toward background QSOs for the first time. I will also discuss prospects for new constraints on the sizes of CGM absorbers, and provide a first glimpse into the small-scale distribution of this diffuse material. Such measurements represent important steps toward a complete, detailed empirical picture of the CGM.