Correlation Between the Total Gravitating Mass of Groups and Clusters and the Supermassive Black Hole Mass of Brightest Galaxies

TL;DR

This study investigates the relationship between supermassive black hole masses in brightest cluster galaxies and the total gravitating mass of their host galaxy groups or clusters, finding a tighter correlation with virial temperature than with stellar bulge mass.

Contribution

It introduces a new correlation between black hole mass and cluster virial temperature, showing a tighter relation than previous bulge-based correlations, supported by observational data and simulations.

Findings

Black hole mass correlates strongly with cluster virial temperature.

The $M_{BH} - kT$ relation has less scatter than the $M_{BH} - M_{bulge}$ relation.

Simulations reproduce the observed relations with smaller scatter.

Abstract

Supermassive black holes (BHs) residing in the brightest cluster galaxies are over-massive relative to the stellar bulge mass or central stellar velocity dispersion of their host galaxies. As BHs residing at the bottom of the galaxy cluster's potential well may undergo physical processes that are driven by the large-scale characteristics of the galaxy clusters, it is possible that the growth of these BHs is (indirectly) governed by the properties of their host clusters. In this work, we explore the connection between the mass of BHs residing in the brightest group/cluster galaxies (BGGs/BCGs) and the virial temperature, and hence total gravitating mass, of galaxy groups/clusters. To this end, we investigate a sample of 17 BGGs/BCGs with dynamical BH mass measurements and utilize XMM-Newton X-ray observations to measure the virial temperatures and infer the $M_{\rm 500}$ mass of the galaxy groups/clusters. We find that the $M_{\rm BH} - kT$ relation is significantly tighter and exhibits smaller scatter than the $M_{\rm BH} - M_{\rm bulge}$ relations. The best-fitting power-law relations are $ \log_{10} (M_{\rm BH}/10^{9} \ \rm{M_{\odot}}) = 0.20 + 1.74 \log_{10} (kT/1 \ \rm{keV}) $ and $ \log_{10} (M_{\rm BH}/10^{9} \ \rm{M_{\odot}}) = -0.80 + 1.72 \log_{10} (M_{\rm bulge}/10^{11} \ M_{\odot})$. Thus, the BH mass of BGGs/BCGs may be set by physical processes that are governed by the properties of the host galaxy group/cluster. These results are confronted with the Horizon-AGN simulation, which reproduces the observed relations well, albeit the simulated relations exhibit notably smaller scatter.