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arXiv · 0901.2517

Evidence of a link between the evolution of clusters and their AGN fraction

Caroline van Breukelen·Chris Simpson·Steve Rawlings·Masayuki Akiyama·David Bonfield·Lee Clewley·Matt J. Jarvis·Tom Mauch·Tony Readhead·Ann-Marie Stobbart·Mark Swinbank·Mike Watson
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Abstract

We discuss the optical properties, X-ray detections, and Active Galactic Nucleus (AGN) populations of four clusters at z ~ 1 in the Subaru-XMM Deep Field (SXDF). The velocity distribution and plausible extended X-ray detections are examined, as well as the number of X-ray point sources and radio sources associated with the clusters. We find that the two clusters that appear virialised and have an extended X-ray detection contain few, if any, AGN, whereas the two pre-virialised clusters have a large AGN population. This constitutes evidence that the AGN fraction in clusters is linked to the clusters' evolutionary stage. The number of X-ray AGN in the pre-virialised clusters is consistent with an overdensity of factor ~ 200; the radio AGN appear to be clustered with a factor of three to six higher. The median K-band luminosities of L_K = 1.7 +/- 0.7 L* for the X-ray sources and L_K = 2.3 +/- 0.1 L* for the radio sources support the theory that these AGN are triggered by galaxy interaction and merging events in sub-groups with low internal velocity distributions, which make up the cluster environment in a pre-virialisation evolutionary stage.

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Caroline van Breukelen, Chris Simpson, Steve Rawlings, Masayuki Akiyama, David Bonfield, Lee Clewley, Matt J. Jarvis, Tom Mauch, Tony Readhead, Ann-Marie Stobbart, Mark Swinbank, Mike Watson. 2009-01-16. Evidence of a link between the evolution of clusters and their AGN fraction. https://doi.org/10.1111/j.1365-2966.2009.14513.x

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