The most massive black holes on the Fundamental Plane of black hole accretion. Issue 1 (30th October 2017)

• Record Type: Journal Article
• Authors: Mezcua, M.; Hlavacek-Larrondo, J.; Lucey, J. R.; Hogan, M. T.; Edge, A. C.; McNamara, B. R.
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 474:Issue 1(2018)
• Page Start: 1342
• Page End: 1360
• Publication Date: 2017-10-30
• Subjects: accretion, accretion discs -- black hole physics -- galaxies: active -- galaxies: clusters: general -- galaxies: jets -- X-rays: galaxies: clusters; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stx2812
• Languages: English
• ISSNs: 0035-8711

Abstract

Abstract: 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 $L_\mathrm{X} \propto L_\mathrm{R}^{0.75 \pm 0.08}$, 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 M BH – M K 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 >10 10 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.