Extracting the Dark Matter Profile of a Relaxed Galaxy Cluster

Abstract

Knowledge of the structure of galaxy clusters is essential for an understanding of large scale structure in the universe, and may provide important clues to the nature of dark matter. Moreover, the shape of the dark matter distribution in the cluster core may offer insight into the structure formation process. Unfortunately, cluster cores also tend to be the site of complicated astrophysics. X-ray imaging spectroscopy of relaxed clusters, a standard technique for mapping their dark matter distributions, is often complicated by the presence of cool components in cluster cores, and the dark matter profile one derives for a cluster is sensitive to assumptions made about the distribution of this component. In addition, fluctuations in the temperature measurements resulting from normal statistical variance can produce results which are unphysical. We present here a procedure for extracting the dark matter profile of a spherically symmetric, relaxed galaxy cluster which deals with both of these complications. We apply this technique to a sample of galaxy clusters observed with the Chandra X-ray Observatory, and comment on the resulting mass profiles. For some of the clusters we compare their masses with those derived from weak and strong gravitational measurements.