Joint Astrophysics Colloquium

Joint Astrophysics Seminar

The Inner Workings of Early-Type Galaxies:
Supermassive Black Holes and Stellar Nuclei

Laura Ferrarese

HIA NRC Victoria

Stellar and gas dynamical studies in an ever-increasing number of galaxies have established that many — and perhaps all — luminous galaxies contain central supermassive black holes (SBHs). Following the discovery that the SBH masses correlate with various properties of the host galaxy — such as bulge luminosity, mass, velocity dispersion, light concentration, and halo circular velocity — it has become widely accepted that SBH and galaxy formation are closely entwined.

More recently, a large imaging survey with the Hubble Space Telescope has shown that 50 to 80% of low- and intermediate-luminosity galaxies contain a compact stellar nucleus at their center, regardless of host galaxy morphological type. I will discuss the connection between stellar nuclei, SBHs and host galaxies, and argue that a generic by-product of galaxy formation is the creation of a “central massive object” (CMO) — either a SBH or a compact stellar nucleus — that contains a mean fraction, ~0.2%, of the total galactic mass. In galaxies with masses greater than a few tens of billion of solar masses, SBHs might be the dominant mode of CMO formation.