I will present results from a program to understand the distribution of baryons in nearby galaxy clusters and groups, as well as the properties of their central galaxies. A main focus of this work is to quantify the total baryon fraction in these systems. If galaxy clusters are indeed fair samples of the universe, then a basic expectation is that the baryon fraction in clusters and groups should reflect the universal value. Observed shortfalls have therefore led to proposals for missing baryons in a warm gas component, as well as other more controversial interpretations. In this work we quantify the total stellar baryon fraction, including stars in both galaxies and the intracluster light, and combine these data with published measurements of the hot baryon fraction in the intracluster medium (ICM). We find that the total baryon fraction is independent of cluster mass, with no compelling evidence for missing baryons. I will also present related results from this program pertaining to cluster galaxy evolution and chemical enrichment of the intracluster medium.
Received April 9, 2008