Can Supermassive Black Holes Sufficiently Heat Cool Cores of Galaxy Clusters?

Abstract

The activities of a supermassive black hole or active galactic nucleus in the central galaxy of a cluster of galaxies have been promising candidates for the heating sources of cool cluster cores. We estimate the masses of black holes using known correlations between the mass of a black hole and the velocity dispersion or the luminosity of the host galaxy. We find that the masses are ~108-109 M☉ and the central X-ray luminosities of the host clusters (the strength of the cooling flow) are well below the Eddington luminosities. However, we do not find a correlation between the mass and the central X-ray luminosity of the host cluster. If the heating is stable, this seems to contradict a simple expectation if a supermassive black hole is the main heating source of a cluster core. Moreover, if we assume a canonical energy conversion rate (10%), black holes alone would be unable to sufficiently heat the clusters with strong centrally peaked X-ray emission (massive cooling flows) over the lifetime of cluster cores. These results may indicate that massive cooling flows are a transient phenomenon, perhaps because the black holes are activated periodically. Alternatively, in the massive cooling flow clusters, the energy conversion rate may be larger than 10%, that is, the black holes may be Kerr black holes.