Supermassive black holes do not correlate with galaxy disks or pseudobulges

TL;DR

This study shows that supermassive black holes are strongly linked to galaxy bulges but not to disks or pseudobulges, indicating different growth modes and coevolution processes.

Contribution

It provides new classifications of pseudobulges and combines data to clarify black hole correlations, revealing two distinct growth modes.

Findings

Black holes correlate with bulges but not with disks or pseudobulges.

Black hole growth in bulges is driven by mergers and rapid accretion.

Black hole growth in pseudobulges and disks is low-level and stochastic.

Abstract

The masses of supermassive black holes are known to correlate with the properties of the bulge components of their host galaxies. In contrast, they appear not to correlate with galaxy disks. Disk-grown pseudobulges are intermediate in properties between bulges and disks. It has been unclear whether they do or do not correlate with black holes in the same way that bulges do, because too few pseudobulges were classified to provide a clear result. At stake are conclusions about which parts of galaxies coevolve with black holes, possibly by being regulated by energy feedback from black holes. Here we report pseudobulge classifications for galaxies with dynamically detected black holes and combine them with recent measurements of velocity dispersions in the biggest bulgeless galaxies. These data confirm that black holes do not correlate with disks and show that they correlate little or not at all with pseudobulges. We suggest that there are two different modes of black hole feeding. Black holes in bulges grow rapidly to high masses when mergers drive gas infall that feeds quasar-like events. In contrast, small black holes in bulgeless galaxies and galaxies with pseudobulges grow as low-level Seyferts. Growth of the former is driven by global processes, so the biggest black holes coevolve with bulges, but growth of the latter is driven locally and stochastically, and they do not coevolve with disks and pseudobulges.