2010ApJ...710..783R

Gravitational interactions between galaxies are widely believed to be the principal mechanism responsible for triggering non-thermal activity in galactic nuclei. We investigate the connection between interacting galaxies and active galactic nuclei (AGNs) in the local universe by comparing the clustering properties of their environments on 0.5 Mpc scales, as quantified by the amplitude of the spatial cross-correlation function. If a direct evolutionary relationship exists, the samples should be situated in environments that are statistically similar. It was previously found that a sample of 33 Seyfert galaxies with z ≤ 0.05 is located in environments comparable to those of isolated field galaxies. The analysis presented here reveals that a well-matched sample of 52 strongly interacting galaxy systems are preferentially situated in regions more consistent with an Abell Richness Class between 0 and 1. The apparent dissimilarity in the environments thus provides a strong argument against a causal link between major galaxy interactions and Seyfert activity. In contrast, we find that the environments of luminous quasars with z ≤ 1 exhibit a range of richness levels that are more consistent with the interacting galaxies, suggesting that these objects could be triggered by interactions. Together the results presented here indicate that the relative importance of different mechanisms in initiating nuclear activity may vary with AGN luminosity.