Relations Between Central Black Hole Mass and Total Galaxy Stellar Mass in the Local Universe

TL;DR

This study explores the relationship between central black hole mass and total galaxy stellar mass in the local universe, revealing a proportional correlation with a notably low BH-to-stellar mass ratio, impacting high-redshift and simulation studies.

Contribution

It provides a comprehensive analysis of the BH-stellar mass relation using a large local galaxy sample, including AGNs and dynamical BH measurements, with consistent stellar mass estimation.

Findings

BH mass correlates with total stellar mass in AGN host galaxies.

The BH-to-stellar mass ratio is approximately 0.025%.

Relation normalization is lower than that of early-type galaxies.

Abstract

Scaling relations between central black hole (BH) mass and host galaxy properties are of fundamental importance to studies of BH and galaxy evolution throughout cosmic time. Here we investigate the relationship between BH mass and host galaxy total stellar mass using a sample of 262 broad-line active galactic nuclei (AGN) in the nearby Universe (z < 0.055), as well as 79 galaxies with dynamical BH masses. The vast majority of our AGN sample is constructed using Sloan Digital Sky Survey spectroscopy and searching for Seyfert-like narrow-line ratios and broad H-alpha emission. BH masses are estimated using standard virial techniques. We also include a small number of dwarf galaxies with total stellar masses M_stellar < 10^9.5 Msun and a sub-sample of the reverberation-mapped AGNs. Total stellar masses of all 341 galaxies are calculated in the most consistent manner feasible using color-dependent mass-to-light ratios. We find a clear correlation between BH mass and total stellar mass for the AGN host galaxies, with M_BH proportional to M_stellar, similar to that of early-type galaxies with dynamically-detected BHs. However, the relation defined by the AGNs has a normalization that is lower by more than an order of magnitude, with a BH-to-total stellar mass fraction of M_BH/M_stellar ~ 0.025% across the stellar mass range 10^8 < M_stellar/Msun < 10^12. This result has significant implications for studies at high redshift and cosmological simulations in which stellar bulges cannot be resolved.