Abstract
Despite the importance of Active Galactic Nuclei (AGN) in galaxy evolution,
the mechanisms that fuel AGN activity remain poorly understood. Theoretical
models suggest that major mergers of galaxies contribute strongly to AGN
fuelling, particularly at high AGN luminosities. The connection between mergers
and AGN activity has therefore been widely studied, although with contradictory
results. Some studies find a strong connection between mergers and AGN, while
others find merger fractions in AGN hosts to match those in the inactive galaxy
population. To address these apparent contradictions, I present a complete and
systematic analysis of detected merger fractions in AGN hosts from the
literature. I assess if discrepancies between studies are indicative of
systematic uncertainties and biases and analyse the detected merger fraction as
a function of luminosity, redshift, and AGN selection method. X-ray selected
AGN samples show comparable detected merger fractions across studies and major
mergers do not dominate triggering in this AGN population. On the other hand,
signatures of significant merger contribution to the AGN population are
observed in a small fraction of primarily radio selected and reddened AGN
samples. It is unclear if this is due to observational biases or physical
differences in the host galaxies. There is no correlation between the detected
merger fraction and AGN luminosity. This lack of correlation between detected
merger fraction and AGN luminosity, which has previously been reported in the
literature, cannot be explained by systematic uncertainties and observational
biases.
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