DISCRETE X-RAY SOURCES IN GALAXY CLUSTERS

Анотація

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.