| Abstract: | Galaxy formation and evolution is tied to the physical state of gas in the circumgalactic medium (CGM) and its interface with the intergalactic medium (IGM), which is determined by the complex interplay between inflows from the IGM and galaxy feedback. Therefore, a comprehensive understanding of the physical conditions of gas within and surrounding galaxies is of paramount importance to understanding the physical processes that regulate galaxy formation and evolution. Numerous efforts to trace the diffuse gas seen in the quasar absorption line have revealed that intervening metal absorbers arise from multiple pathways, including gas inflows and outflows, the intragroup medium, and cool stripped gas from environmental processes. In particular, MgII absorbers, which trace cool, 10^4K, metal-rich gas, are frequently observed across a wide range of impact parameters, up to 200 kpc. However, the notion that the absorption is caused by galaxies at close impact parameters remains viable because it is highly challenging to find such faint galaxies in the glare of a bright background quasar. I will discuss the possible origin of intervening metal absorbers, the distribution of gas in the circumgalactic medium, and how it relates to the absorber properties in general over a wide range of redshifts of 0.4 < z < 1.0 and stellar masses from on our recent efforts based on SDSS survey and imaging data from DESI Legacy Imaging Surveys. |
