case western reserve university



The Distribution of Baryons in Galaxy Clusters and Groups

Anthony Gonzalez (University of Florida)

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 of missing baryons in a warm gas component, as well as other more controversial interpretations. I will present the results of 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 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, galaxy structure, and chemical enrichment of the ICM.