The circumgalactic medium is crucially linked to galaxy formation and evolution, as well as the enrichment of the intergalactic medium. The COS-Halos survey uncovered a large reservoir of metal-enriched, cool gas in the circumgalactic medium of both star-forming and passive galaxies, reaching out to very large scales. Processes that can supply enriched gas to the circumgalactic medium remain uncertain, and many proposed scenarios that can reproduce one aspect of the observations have problems reproducing other aspects. Any model seeking to explain the observations must account for (1) a large amount of gas, (2) relatively slow gas velocities, (3) a high degree of metal enrichment, (4) the similarity between star-forming and passive galaxies, and (5) the temperature and densities of the circumgalactic medium gas. I will show that a simple one-dimensional model for a galactic wind-driven bubble can account for many of these observed properties. I present masses, velocities, column density distributions, and absorption line velocities and line widths of the shell and show that my model can reproduce COS-Halos observations of low-ionization state metal absorption lines around both star-forming and passive galaxies.
