PROBING LOW-REDSHIFT GALAXIES USING QUASAR ABSORPTION LINES WITH AN EMPHASIS ON CA II ABSORPTION 

A successful and complete theory of galaxy formation and evolution must not only explain the properties of the luminous parts of galaxies, but must also account for the properties and evolution of the gaseous structures associated with them. A powerful and unique probe of the properties and evolution of the circumgalactic and galactic gaseous environments of galaxies is provided by the absorption lines they cause in the spectra of background quasars. In this thesis talk, I will present results on using quasar absorption lines to study gas in the lower-redshift Universe. In particular, I will briefly describe the first Hubble Space Telescope quasar absorption line study to search for absorbing gas in the nearby Great Spiral Galaxy in Andromeda, M31. While galaxies in the distant universe can normally be probed with only one quasar sightline, this study utilized 10 quasar sightlines. For the remainder and majority of the thesis talk, I will describe results on using the rare CaII absorbers identified in Sloan Digital Sky Survey quasar spectra to survey the properties and evolution of gas in the most recent 8.8 Gyrs of our cosmic history. This is the largest survey for CaII quasar absorption lines ever performed, resulting in the discovery of 435 absorbers. I will discuss their statistics, their metal abundances and dust properties, and their association with galaxies. Among other findings, this work has revealed the existence of two populations of CaII absorbers.