Journal Article

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 and Mike Watson

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 395, issue 1, pages 11-27
Published in print May 2009 | ISSN: 0035-8711
Published online April 2009 | e-ISSN: 1365-2966 | DOI:
Evidence of a link between the evolution of clusters and their AGN fraction

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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 virialized and have an extended X-ray detection contain few, if any, AGN, whereas the two pre-virialized 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-virialized clusters is consistent with an overdensity of a factor of ∼200; the radio AGN appear to be clustered with a factor of 3 to 6 higher. The median K-band luminosities of LK= 1.7 ± 0.7 L* for the X-ray sources and LK= 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-virialization evolutionary stage.

Keywords: galaxies: active; galaxies: clusters: general; radio continuum: galaxies; X-rays: galaxies; X-rays: galaxies: clusters

Journal Article.  8780 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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