The role of mergers and gas accretion in black hole growth and galaxy evolution

TL;DR

This study uses a semi-analytic model to explore how mergers and gas accretion influence the growth of supermassive black holes and their host galaxies, emphasizing the dominant role of quasar-mode accretion during mergers.

Contribution

It demonstrates that quasar-mode accretion during mergers is the primary driver of SMBH growth and highlights the significant role of mergers in galaxy evolution compared to normal galaxies.

Findings

Quasar-mode accretion during mergers dominates SMBH growth.

Mergers are more influential in SMBH host galaxy growth than in normal galaxies.

The SMBH-host galaxy scaling relation is shaped by combined effects of accretion and mergers.

Abstract

We use a semi-analytic galaxy formation model to study the co-evolution of supermassive black holes (SMBHs) with their host galaxies. Although the coalescence of SMBHs is not important, the quasar-mode accretion induced by mergers plays a dominant role in the growth of SMBHs. Mergers play a more important role in the growth of SMBH host galaxies than in the SMBH growth. It is the combined contribution from quasar mode accretion and mergers to the SMBH growth and the combined contribution from starburst and mergers to their host galaxy growth that determine the observed scaling relation between the SMBH masses and their host galaxy masses. We also find that mergers are more important in the growth of SMBH host galaxies compared to normal galaxies which share the same stellar mass range as the SMBH host galaxies.