Chandra X-ray Observations of Galaxies in an Off-Center Region of the Coma Cluster

Abstract

We have performed a pilot Chandra survey of an off-center region of the Coma cluster to explore the X-ray properties and Luminosity Function of normal galaxies. We present results on 13 Chandra-detected galaxies with optical photometric matches, including four spectroscopically-confirmed Coma-member galaxies. All seven spectroscopically confirmed giant Coma galaxies in this field have detections or limits consistent with low X-ray to optical flux ratios (fX/fR < 10^-3). We do not have sufficient numbers of X-ray detected galaxies to directly measure the galaxy X-ray Luminosity Function (XLF). However, since we have a well-measured optical LF, we take this low X-ray to optical flux ratio for the 7 spectroscopically confirmed galaxies to translate the optical LF to an XLF. We find good agreement with Finoguenov et al. (2004), indicating that the X-ray emission per unit optical flux per galaxy is suppressed in clusters of galaxies, but extends this work to a specific off-center environment in the Coma cluster. Finally, we report the discovery of a region of diffuse X-ray flux which might correspond to a small group interacting with the Coma Intra-Cluster Medium (ICM).