Evidence for a moderate spin from X-ray reflection of the high-mass supermassive black hole in the cluster-hosted quasar H1821+643

Abstract

We present an analysis of deep $Chandra$ Low-Energy and High-Energy Transmission Grating archival observations of the extraordinarily luminous radio-quiet quasar H1821+643, hosted by a rich and massive cool-core cluster at redshift $z=0.3$. These datasets provide high-resolution spectra of the AGN at two epochs, free from contamination by the intracluster medium and from the effects of photon pile-up, providing a sensitive probe of the iron-$K$ band. At both epochs, the spectrum is well described by a power-law continuum plus X-ray reflection from both the inner accretion disc and cold, slowly-moving distant matter. Adopting this framework, we proceed to examine the properties of the inner disc and the black hole spin. Using Markov chain Monte Carlo (MCMC) methods, we combine constraints from the two epochs assuming that the black hole spin, inner disc inclination, and inner disc iron abundance are invariant. The black hole spin is found to be modest, with a 90$\%$ credible range of $a^{\ast }=0.62_{-0.37}^{+0.22}$; and, with a mass $M_{\mathrm{BH}}$ in the range $\log (M_{\mathrm{BH}}/M_{\odot })\sim 9.2-10.5$, this is the most massive black hole candidate for which a well-defined spin constraint has yet been obtained. The modest spin of this black hole supports previous suggestions that the most massive black holes may grow via incoherent or chaotic accretion and/or SMBH-SMBH mergers.

13 pages, 8 figures, 3 tables. Accepted for publication in MNRAS. Amended to include two missing references

References in corpus (18)

• HI4PI: A full-sky HI survey based on EBHIS and GASS
• The role of the reflection fraction in constraining black hole spin
• On the use of C-stat in testing models for X-ray spectra
• X-ray cavities in a sample of 83 SPT-selected clusters of galaxies: Tracing the evolution of AGN feedback in clusters of galaxies out to z=1.2
• The host galaxies of luminous quasars
• Multi-dimensional modelling of X-ray spectra for AGN accretion-disk outflows
• New constraints on light Axion-Like Particles using Chandra Transmission Grating Spectroscopy of the powerful cluster-hosted quasar H1821+643
• The Origin of the Intrinsic Scatter in the Relation Between Black Hole Mass and Bulge Luminosity for Nearby Active Galaxies
• A giant radio halo in the cool core cluster CL1821+643
• Detection of the Missing Baryons toward the Sightline of H1821+643
• The effect of the quasar H1821+643 on the surrounding intracluster medium: revealing the underlying cooling flow
• On Constraining the Growth History of Massive Black Holes via Their Distribution on the Spin-Mass Plane
• The X-ray Disk/Wind Degeneracy in AGN
• The X-ray spectrum of the cooling-flow quasar H1821+643 : A massive black hole feeding off the intracluster medium
• How unusual is the cool-core radio halo cluster CL1821+643 ?
• A Comparison of Two Methods for Estimating Black Hole Spin in Active Galactic Nuclei
• Detection of a possible multiphase ultra-fast outflow in IRAS 13349+2438 with NuSTAR and XMM-Newton
• XMM-Newton view of the double-peaked Fe K-alpha complex in E1821+643