Relationship of Black Holes to Bulges

TL;DR

This paper discusses the relationship between supermassive black holes and galactic bulges, highlighting the discovery of the M-sigma relation that links black hole mass to bulge velocity dispersion and resolves previous measurement discrepancies.

Contribution

It reviews the development and implications of the M-sigma relation, establishing a consistent understanding of black hole and bulge co-evolution.

Findings

Excellent agreement among different black hole mass estimation techniques.

The M-sigma relation confirms a tight correlation between black hole mass and bulge velocity dispersion.

Implications for black hole formation theories are discussed.

Abstract

Supermassive black holes appear to be uniquely associated with galactic bulges. The mean ratio of black hole mass to bulge mass was until recently very uncertain, with ground based, stellar kinematical data giving a value roughly an order of magnitude larger than other techniques. The discrepancy was resolved with the discovery of the M-sigma relation, which simultaneously established a tight corrrelation between black hole mass and bulge velocity dispersion, and confirmed that the stellar kinematical mass estimates were systematically too large due to failure to resolve the black hole's sphere of influence. There is now excellent agreement between the various techniques for estimating the mean black hole mass, including dynamical mass estimation in quiescent galaxies; reverberation mapping in active galaxies and quasars; and computation of the mean density of compact objects based on integrated quasar light. Implications of the M-sigma relation for the formation of black holes are discussed.