DISCRETE X-RAY SOURCES IN GALAXY CLUSTERS

Abstract

Current studies of extragalactic X-ray sources using data from orbital observatory XMM- Newton are at the front line of X-ray astronomy. Resolution capacity of the observatory instruments enable to detect separate X-ray sources in the close galaxies. In this study we used data from recently published 4XMM-DR9 catalog. This catalog contains 550124 unique sources covering 2,85% of the sky. The main type of extended extragalactic X-ray source is hot halo of galaxy cluster. Such objects are important for astrophysics in the tasks of revealing dark matter distribution, galaxy formation and different cosmology studies. At the same time, some images of the galaxy clusters contain small scale pointlike X-ray sources scattered around the clusters or their halos. In many cases the nature of such objects is not clear yet and require more detailed studies. Furthermore, energy flux detection threshold of such objects is limited to a great extend not only by the instruments on board of the XMM- Newton observatory but the natural sky background radiation, which is at the level of 10 −13 Wm −2 sr −1 both for XMM cameras and the sky background. Using Hyperleda database we revealed 16 galaxy clusters among the bright XMM sources. Images of the two galaxy clusters demonstrate bright galaxy cores. These clusters are galaxy group NGC 507 and Coma cluster where nucleus of galaxy NGC 4889 was clearly detected. We also analyzed X-ray images of 14 other X-ray clusters but had not found AGNs there. Out of the above mentioned 16 clusters in the 7 of them we have found 30 pointlike X-ray sources. These sources are presumably mainly AGNs within these clusters. From the other side, they could be also more distant X-ray objects.