The X-ray luminous cluster underlying the bright radio-quiet quasar H1821+643

We present a Chandra observation of the only low redshift, z = 0.299, galaxy cluster to contain a highly luminous radio-quiet quasar, H1821+643. By simulating the quasar point spread function, we subtract the quasar contribution from the cluster core and determine the physical properties of the cluster gas down to 3arcsec (15kpc) from the point source. The temperature of the cluster gas decreases from 9.0 +/- 0.5 down to 1.3 +/- 0.2keV in the centre, with a short central radiative cooling time of 1.0 +/- 0.1Gyr, typical of a strong cool-core cluster. The X-ray morphology in the central 100kpc shows extended spurs of emission from the core, a small radio cavity and a weak shock or cold front forming a semicircular edge at ~15arcsec radius. The quasar bolometric luminosity was estimated to be ~2 × 10⁴⁷ergs^-1, requiring a mass accretion rate of ~40M_solaryr^-1, which corresponds to half the Eddington accretion rate. We explore possible accretion mechanisms for this object and determine that Bondi accretion, when boosted by Compton cooling of the accretion material, could provide a significant source of the fuel for this outburst. We consider H1821+643 in the context of a unified active galactic nucleus (AGN) accretion model and, by comparing H1821+643 with a sample of galaxy clusters, we show that the quasar has not significantly affected the large-scale cluster gas properties.