Description
Galaxy interactions and mergers have been known to be an important method of triggering central supermassive black holes into active galactic nuclei (AGN). One method to identify these systems is by looking for close pairs of galaxies. To study environmental effects on AGN triggering in dense galaxy environments, we use a catalog of infrared-bright selected AGN along the lines of sight to galaxy clusters in the South Pole Telescope (SPT) cluster surveys spanning a redshift range of $0.15 \lesssim z \lesssim 1.7$. We identify close pairs of galaxies hosting AGN where we find that the density of close pairs rises to $\sim15\%$ of all pairs of galaxies in the outskirts of the clusters at $\gtrsim 1.5 r_{500}$. This is an indication that while the fraction of AGN close pairs are on average suppressed in the cores of the clusters, they are significant in the outer regions of the clusters. This could be due to galaxy–galaxy interactions or mergers occurring in the infall region of clusters.
