The X-ray luminosity function of galaxies in the Coma cluster

The XMM-Newton survey of the Coma cluster of galaxies covers an area of 1.86 square degrees with a mosaic of 16 pointings and has a total useful integration time of 400 ks. Detected X-ray sources with extent less than 10^'' were correlated with cataloged galaxies in the Coma cluster region. The redshift information, which is abundant in this region of the sky, allowed us to separate cluster members from background and foreground galaxies. For the background sources, we recover a typical Log N-Log S in the flux range 10^-15-10^-13 ergs s^-1 cm^-2 in the 0.5-2.0 keV band. The X-ray emission from the cluster galaxies exhibits X-ray colors typical of thermal emission. The luminosities of Coma galaxies lie in the 10³⁹-10⁴¹ ergs s^-1 interval in the 0.5-2.0 keV band. The luminosity function of Coma galaxies reveals that their X-ray activity is suppressed with respect to the field by a factor of 5.6, indicating a lower level of X-ray emission for a given stellar mass.