X-ray Bright Active Galactic Nuclei in Massive Galaxy Clusters I: Number Counts and Spatial Distribution. (arXiv:1209.2132v1 [astro-ph.CO]):
We present an analysis of the X-ray bright point source population in 43
massive clusters of galaxies observed with the Chandra X-ray Observatory. We
have constructed a catalog of 4210 rigorously selected X-ray point sources in
these fields, which span a survey area of 4.2 square degrees. This catalog
reveals a clear excess of sources when compared to deep blank-field surveys,
which amounts to roughly 1 additional source per cluster, likely Active
Galactic Nuclei (AGN) associated with the clusters. The excess sources are
concentrated within the virial radii of the clusters, with the largest excess
observed near the cluster centers. The average radial profile of the excess
X-ray sources of the cluster are well described by a power law (N(r) ~ r^\beta)
with an index of \beta ~ -0.5. An initial analysis using literature results on
the mean profile of member galaxies in massive X-ray selected clusters
indicates that the fraction of galaxies hosting X-ray AGN rises with increasing
clustercentric radius, being approximately 5 to 10 times higher near the virial
radius than in the central regions. This trend is qualitatively similar to that
observed for star formation in cluster member galaxies.
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