Evidence of a link between the evolution of clusters and their AGN fraction |
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| Authors: | 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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| Institution: | Physics &Astronomy, University College London, Gower Street, London WC1E 6BT;Astrophysics, Department of Physics, Keble Road, Oxford OX1 3RH;Astrophysics Research Institute, Liverpool John Moores University, Twelve Quays House, Egerton Wharf, Birkenhead CH41 1LD;Subaru Telescope, National Astronomical Observatory of Japan, 650 North A'ohoku Place, Hilo, HI 96720, USA;NASA's Goddard Space Flight Center, Greenbelt, MD 20771, USA;Centre for Astrophysics, Science &Technology Research Institute, University of Hertfordshire, Hatfield AL10 9AB;Owens Valley Radio Observatory, California Institute of Technology, Pasadena, CA 91125, USA;X-ray Astronomy Group, Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH;Institute for Computational Cosmology, Department of Physics, Durham University, Durham DH1 3LE |
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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 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. |
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| Keywords: | galaxies: active galaxies: clusters: general radio continuum: galaxies X-rays: galaxies X-rays: galaxies: clusters |
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