# Spatially Offset Active Galactic Nuclei. II: Triggering in Galaxy Mergers

## TL;DR

This study investigates how galaxy mergers influence active galactic nucleus (AGN) activation, finding that dual AGN are more likely to be triggered at closer nuclear separations and later merger stages, with implications for understanding AGN fueling.

## Contribution

It systematically compares offset and dual AGN in galaxy mergers, revealing their dependence on merger stage and nuclear separation, and provides the first detailed analysis at sub-kiloparsec scales.

## Key findings

- Dual AGN fraction increases with merger proximity.
- Offset and dual AGN are similarly prevalent at small separations.
- AGN observability peaks at nuclear separations below 1 kpc.

## Abstract

Galaxy mergers are likely to play a role in triggering active galactic nuclei (AGN), but the conditions under which this process occurs are poorly understood. In Paper I, we constructed a sample of spatially offset X-ray AGN that represent galaxy mergers hosting a single AGN. In this paper, we use our offset AGN sample to constrain the parameters that affect AGN observability in galaxy mergers. We also construct dual AGN samples with similar selection properties for comparison. We find that the offset AGN fraction shows no evidence for a dependence on AGN luminosity, while the dual AGN fractions show stronger evidence for a positive dependence, suggesting that the merger events forming dual AGN are more efficient at instigating accretion onto supermassive black holes than those forming offset AGN. We also find that the offset and dual AGN fractions both have a negative dependence on nuclear separation and are similar in value at small physical scales. This dependence may become stronger when restricted to high AGN luminosities, though a larger sample is needed for confirmation. These results indicate that the probability of AGN triggering increases at later merger stages. This study is the first to systematically probe down to nuclear separations of <1 kpc (~0.8 kpc) and is consistent with predictions from simulations that AGN observability peaks in this regime. We also find that the offset AGN are not preferentially obscured compared to the parent AGN sample, suggesting that our selection may be targeting galaxy mergers with relatively dust-free nuclear regions.