Enhancement of AGN in a protocluster at z=1.6

Krishnan, Charutha, Hatch, Nina A., Almaini, Omar, Kocevski, Dale, Cooke, Elizabeth A., Hartley, William G., Hasinger, Guenther, Maltby, David T., Muldrew, Stuart I. and Simpson, Chris (2017) Enhancement of AGN in a protocluster at z=1.6. Monthly Notices of the Royal Astronomical Society, 470 (2). pp. 2170-2178. ISSN 1365-2966

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We investigate the prevalence of AGN in the high-redshift protocluster Cl 0218.3–0510 at z = 1.62. Using imaging from the Chandra X-ray Telescope, we find a large overdensity of AGN in the protocluster; a factor of 23±9 times the field density of AGN. Only half of this AGN overdensity is due to the overdensity of massive galaxies in the protocluster (a factor of 11±2), as we find that 17+6−5% of massive galaxies (M∗ > 1010M⊙) in the protocluster host an X-ray luminous AGN, compared to 8±1% in the field. This corresponds to an enhancement of AGN activity in massive protocluster galaxies by a factor of 2.1±0.7 at 1.6s significance. We also find that the AGN overdensity is centrally concentrated, located within 3 arcmin and most pronounced within 1 arcmin of the centre of the protocluster. Our results confirm that there is a reversal in the local anti-correlation between galaxy density and AGN activity, so there is an enhancement of AGN in high-redshift protoclusters. We compare the properties of AGN in the protocluster to the field and find no significant differences in the distributions of their stellar mass, X-ray luminosity, or hardness ratio. We therefore suggest that triggering mechanisms are similar in both environments, and that the mechanisms simply occur more frequently in denser environments.

Item Type: Article
RIS ID: https://nottingham-repository.worktribe.com/output/862621
Additional Information: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2017 The authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Keywords: galaxies: active – galaxies: clusters: individual: Cl 0218.3−0510
Schools/Departments: University of Nottingham, UK > Faculty of Science > School of Physics and Astronomy
Identification Number: https://doi.org/10.1093/mnras/stx1315
Depositing User: Eprints, Support
Date Deposited: 02 Jun 2017 12:53
Last Modified: 04 May 2020 18:47
URI: https://eprints.nottingham.ac.uk/id/eprint/43363

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