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The most massive black holes on the Fundamental Plane of black hole accretion.

Mezcua, M. and Hlavacek-Larrondo, J. and Lucey, J. R. and Hogan, M. T. and Edge, A. C. and McNamara, B. R. (2018) 'The most massive black holes on the Fundamental Plane of black hole accretion.', Monthly notices of the Royal Astronomical Society., 474 (1). pp. 1342-1360.


We perform a detailed study of the location of brightest cluster galaxies (BCGs) on the Fundamental Plane of black hole (BH) accretion, which is an empirical correlation between a BH X-ray and radio luminosity and mass supported by theoretical models of accretion. The sample comprises 72 BCGs out to z ∼ 0.3 and with reliable nuclear X-ray and radio luminosities. These are found to correlate as LX∝L0.75±0.08R , favouring an advection-dominated accretion flow as the origin of the X-ray emission. BCGs are found to be on average offset from the Fundamental Plane such that their BH masses seem to be underestimated by the MBH–MK relation a factor ∼10. The offset is not explained by jet synchrotron cooling and is independent of emission process or amount of cluster gas cooling. Those core-dominated BCGs are found to be more significantly offset than those with weak core radio emission. For BCGs to on average follow the Fundamental Plane, a large fraction ( ∼ 40 per cent) should have BH masses >1010 M⊙ and thus host ultramassive BHs. The local BH–galaxy scaling relations would not hold for these extreme objects. The possible explanations for their formation, either via a two-phase process (the BH formed first, the galaxy grows later) or as descendants of high-z seed BHs, challenge the current paradigm of a synchronized galaxy–BH growth.

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Publisher statement:This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2017 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Date accepted:26 October 2017
Date deposited:01 March 2018
Date of first online publication:30 October 2017
Date first made open access:01 March 2018

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