Title: Environmentally Driven Galaxy Evolution and Quenching: Insights from the Low-redshift Circumgalactic Medium
Extending an order of magnitude beyond the regions of galaxies shining in starlight, the circumgalactic medium (CGM) serves as a massive reservoir of multiphase gas. Perhaps even more importantly to the lifecycles of galaxies, the processes driving galaxy evolution such as fueling/regulating star formation and the distribution of heavy elements are mediated by the CGM. Thus, the physical conditions and composition of CGM gas bear the imprint as well as dictate this evolution. Using a combination of ultraviolet spectroscopy from the Hubble Space Telescope, large optical ground-based galaxy surveys, and X-ray imaging/spectroscopy, I will characterize the CGM as traced by H I, C IV, and O VI absorption lines across a wide range of halo environments, from isolated dwarf galaxies with Mstars < 10^8 Msun to galaxy clusters with Mhalo > 10^14 Msun. These species reveal strong correlations with their host halo environments: the least massive isolated dwarf galaxies are underabundant in warm, metal-enriched gas (traced by C IV) relative to those with Mstars > 10^9.5 Msun; galaxies normally rich in C IV are devoid of this material if they reside in modestly populated groups; and H I, which is nearly ubiquitous in the CGM of field galaxies, is starkly deficient in galaxy clusters. These results underscore the role of the CGM as the point of contact between a galaxy and its ambient environment and emphasize the necessity of a CGM/environment ‘ecosystem’ perspective in galaxy evolution science.