A Fundamental Relation Between Supermassive Black Holes and Their Host Galaxies

TL;DR

This work demonstrates a remarkably tight correlation between supermassive black hole mass and host bulge velocity dispersion, quantified as M_BH ∝ σ^α with α = 4.8 ± 0.5. Using a carefully curated set of robust BH mass measurements and standardized sigma calibrations, the authors show the M_BH–sigma relation is far tighter than the M_BH–bulge luminosity relation, with negligible intrinsic scatter. The study argues that bulge dynamics, reflected by sigma, govern BH growth and highlights biases in the Magorrian et al. masses that overestimate M_BH in many galaxies. The findings have broad implications for galaxy formation theories and enable predicting M_BH from a single velocity-dispersion measurement with ~30% accuracy.

Abstract

The masses of supermassive black holes correlate almost perfectly with the velocity dispersions of their host bulges, M(BH) ~ sigma^alpha, where alpha =4.8 +/- 0.5$. The relation is much tighter than the relation between M(BH) and bulge luminosity, with a scatter no larger than expected on the basis of measurement error alone. Black hole masses estimated by Magorrian et al. (1998) lie systematically above the M(BH)-sigma relation defined by more accurate mass estimates, some by as much as two orders of magnitude. The tightness of the M(BH)-sigma relation implies a strong link between black hole formation and the properties of the stellar bulge.