A definitive merger-AGN connection at z ∼ 0 with CFIS: mergers have an excess of AGN and AGN hosts are more frequently disturbed

The question of whether galaxy mergers are linked to the triggering ofactive galactic nuclei (AGN) continues to be a topic of considerabledebate. The issue can be broken down into two distinct questions: (1)Can galaxy mergers trigger AGN? (2) Are galaxy mergers the dominant AGNtriggering mechanism? A complete picture of the AGN-merger connectionrequires that both of these questions are addressed with the same dataset. In previous work, we have shown that galaxy mergers selected fromthe Sloan Digital Sky Survey (SDSS) show an excess of both opticallyselected, and mid-IR colour-selected AGN, demonstrating that the answerto the first of the above questions is affirmative. Here, we use thesame optical and mid-IR AGN selection to address the second question, byquantifying the frequency of morphological disturbances in low-surfacebrightness r-band images from the Canada France Imaging Survey (CFIS).Only ?30 per cent of optical AGN host galaxies are morphologicallydisturbed, indicating that recent interactions are not the dominanttrigger. However, almost 60 per cent of mid-IR AGN hosts show signs ofvisual disturbance, indicating that interactions play a more significantrole in nuclear feeding. Both mid-IR and optically selected AGN haveinteracting fractions that are a factor of two greater than a mass andredshift matched non-AGN control sample, an excess that increases withboth AGN luminosity and host galaxy stellar mass.