Event Details

AGN and where to find them: triggering in clusters, groups, and pairs of galaxies

Abstract:

Active Galactic Nuclei (AGN) are found in a wide range of environments from the highest density regions of galaxy clusters to more isolated pairs of galaxies. In this talk, I will focus at first on an apparent (and on-going) conflict in the literature between works that suggest environment is important for the triggering of AGN, and works to the contrary. I will suggest that for clusters of galaxies this could be due to both selection effects, as well as the fact that the time lag between the triggering event and subsequent AGN phase is non-negligible. Further down the mass function, I will show that in groups of galaxies AGN are preferentially located in infalling populations at higher masses, but at lower halo masses there is no difference between core group galaxies and infallers. This is likely due to the frequency of lower speed interactions. I will finally focus on pairs of galaxies to resolve a final conflict in the literature on whether there is any difference between type I and type II AGN fractions in pairs that could potentially violate the AGN unification scheme. We find that AGN unification is a safe interpretation for AGN for the time being.

[If time permits, or there is interest afterward, I will additionally review our very recent work on a Galaxy Zoo related project that showed minor mergers do not fuel LERGs.]