Morphologies of low-redshift AGN host galaxies: what role does AGN luminosity play?

TL;DR

This study compares the morphologies of low-redshift AGN host galaxies with control samples to investigate the role of AGN luminosity, finding no significant link between AGN activity and galaxy mergers across a broad luminosity range.

Contribution

It provides evidence that galaxy mergers are not strongly associated with AGN activity over a wide luminosity range, challenging previous assumptions about their role in triggering AGN.

Findings

No enhanced merger rates in AGN hosts.

No correlation between AGN luminosity and disturbance signs.

Excludes strong AGN-merger connection for most of the AGN population.

Abstract

Mergers of galaxies have been suspected to be a major trigger of AGN activity for many years. However, when compared to carefully matched control samples, AGN host galaxies often show no enhanced signs of interaction. A common explanation for this lack of observed association between AGN and mergers has often been that while mergers are of importance for triggering AGN, they only dominate at the very high luminosity end of the AGN population. In this study, we compare the morphologies of AGN hosts to a carefully matched control sample and particularly study the role of AGN luminosity. We find no enhanced merger rates in AGN hosts and also find no trend for stronger signs of disturbance at higher AGN luminosities. While this study does not cover very high luminosity AGN, we can exclude a strong connection between AGN and mergers over a wide range of AGN luminosities and therefore for a large part of the AGN population.