0 Assigned ID: 190 ----- Attempting Submission 1 (Thu Apr 06 03:16:37 GMT 2017) ----- Environment matters when it comes to galaxy evolution, and the mechanisms driving this evolution are reflected in the diffuse gas residing within the large-scale structures enveloping the cosmic galaxy population. QSO absorption lines effectively probe the circumgalactic medium (CGM) and intragroup and intracluster media, and work thus far hints at profound environmental effects on the CGM. However, sample sizes remain small, and a unifying picture of the gas characteristics across diverse environments has yet to emerge. Within the Sloan Digital Sky Survey, we have identified a sample volume containing a remarkable diversity in large-scale environment with an array of voids, >10,000 groups, several filaments, and 5 clusters, including the Coma Supercluster and CfA Great Wall. Leveraging the Hubble Spectroscopic Legacy Archive (HSLA), we propose a study using >360 background QSOs probing this volume to study the effects of large-scale environment on CGM and intergalactic medium (IGM) gas. The z = 0.019-0.028 spectroscopic galaxy sample is uniformly complete to galaxies L > 0.03 L* and, with the HSLA, produces ~200 galaxy/sightline pairs within 300-kpc impact parameters across a wide range of environmental densities and structures. Upon quantifying the galaxy environment and identifying/measuring the QSO absorption lines at z = 0.019-0.028, we will pursue the following primary science goals: 1. Constrain the CGM/IGM physical conditions across four orders of magnitude in galaxy density 2. Compare ionic abundances and ionization states in the CGM of galaxies in filaments vs. voids 3. Statistically investigate the IGM/CGM gas properties from structure to structure Galaxies and the IGM 0 Regular false true false SUPPORTED