Self-Regulated Star Formation and the Black Hole-Galaxy Bulge Relation

TL;DR

This paper demonstrates that star formation in galaxy bulges is self-regulated by momentum feedback, establishing a natural relation between black hole mass and bulge mass that aligns with observations, and discusses how AGN feedback terminates star formation.

Contribution

It introduces a self-regulation model for bulge star formation via momentum feedback and explains the origin of the black hole-bulge mass relation.

Findings

Bulge star formation is self-regulated by momentum feedback.

The black hole-bulge mass relation is linear and consistent with observations.

AGN feedback can terminate star formation by removing residual gas.

Abstract

We show that star formation in galaxy bulges is self-regulating through momentum feedback, limiting the stellar bulge mass to M_b ~ sigma^4. Together with a black hole mass M_BH ~ sigma^4 set by AGN momentum feedback, this produces a linear M_BH - M_b relation. At low redshift this gives M_BH/M_b ~ 0.001, close to the observed ratio. We show that AGN feedback can remove any remaining gas from the bulge and terminate star formation once the central black hole reaches the M_BH - sigma value, contrary to earlier claims. We find a mild upward deviation from the sigma^4 law at higher redshift and at higher sigma.