# Supermassive black holes in disk-dominated galaxies outgrow their bulges and co-evolve with their host galaxies

## TL;DR

This study shows that supermassive black holes can grow significantly in disk-dominated, merger-free galaxies, challenging the idea that major mergers are essential for black hole and galaxy co-evolution.

## Contribution

It demonstrates that black hole growth and galaxy evolution can occur independently of major mergers, highlighting alternative fundamental processes.

## Key findings

- Black holes in merger-free galaxies are larger than expected from bulge growth.
- Black hole and total stellar mass relations are similar in merger-free and merger-affected galaxies.
- Major mergers are not necessary for significant black hole growth.

## Abstract

The deep connection between galaxies and their supermassive black holes is central to modern astrophysics and cosmology. The observed correlation between galaxy and black hole mass is usually attributed to the contribution of major mergers to both. We make use of a sample of galaxies whose disk-dominated morphologies indicate a major-merger-free history and show that such systems are capable of growing supermassive black holes at rates similar to quasars. Comparing black hole masses to conservative upper limits on bulge masses, we show that the black holes in the sample are typically larger than expected if processes creating bulges are also the primary driver of black hole growth. The same relation between black hole and total stellar mass of the galaxy is found for the merger-free sample as for a sample which has experienced substantial mergers, indicating that major mergers do not play a significant role in controlling the coevolution of galaxies and black holes. We suggest that more fundamental processes which contribute to galaxy assembly are also responsible for black hole growth.