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

Research output: Contribution to journalArticlepeer-review

16 Citations (Scopus)


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.

Original languageEnglish
Pages (from-to)11-27
Number of pages17
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
Publication statusPublished - 2009 May
Externally publishedYes


  • Galaxies: active
  • Galaxies: clusters: general
  • Radio continuum: galaxies
  • X-rays: galaxies
  • X-rays: galaxies: clusters

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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