Revisiting the Scaling Relations of Black Hole Masses and Host Galaxy Properties

TL;DR

This study updates black hole mass scaling relations with new data, revealing differences between galaxy types and profiles, and discusses the scatter and its dependence on galaxy properties.

Contribution

It provides revised scaling relations for black hole masses using an expanded sample and analyzes differences across galaxy types and profiles.

Findings

Early-type galaxies have higher Mbh at given sigma than late types.

Core-profile galaxies have about twice the Mbh of power-law galaxies at same sigma.

Weak evidence for increased scatter in Mbh at lower bulge masses.

Abstract

New kinematic data and modeling efforts in the past few years have substantially expanded and revised dynamical measurements of black hole masses (Mbh) at the centers of nearby galaxies. Here we compile an updated sample of 72 black holes and their host galaxies, and present revised scaling relations between Mbh and stellar velocity dispersion (sigma), V-band luminosity (L), and bulge stellar mass (Mbulge), for different galaxy subsamples. Our best-fitting power law relations for the full galaxy sample are log(Mbh) = 8.32 + 5.64*log(sigma/200 kms), log(Mbh) = 9.23 + 1.11*log(L/10^{11} Lsun), and log(Mbh) = 8.46 + 1.05*log(Mbulge/10^{11} Msun). A log-quadratic fit to the Mbh-sigma relation with an additional term of beta_2*[log(sigma/200 kms)]^2 gives beta_2 = 1.68 +/- 1.82 and does not decrease the intrinsic scatter in Mbh. When the early- and late-type galaxies are fit separately, we obtain similar slopes of 5.20 and 5.06 for the Mbh-sigma relation but significantly different intercepts -- Mbh in early-type galaxies are about 2 times higher than in late types at a given sigma. Within early-type galaxies, our fits to Mbh(sigma) give Mbh that is about 2 times higher in galaxies with central core profiles than those with central power-law profiles. Our Mbh-L and Mbh-Mbulge relations for early-type galaxies are similar to those from earlier compilations. When the conventional quadrature method is used to determine the intrinsic scatter in Mbh, our dataset shows weak evidence for increased scatter at Mbulge < 10^{11} Msun or L_V < 10^{10.3} Lsun, while the scatter stays constant for 10^{11} < Mbulge < 10^{12.3} Msun and 10^{10.3} < L_V < 10^{11.5} Lsun. A Bayesian analysis indicates a larger sample of Mbh measurements would be needed to detect any statistically significant trend in the scatter with galaxy properties.