Center for Relativistic Astrophysics (CRA) - Dr. Preethi Nair

Understanding the mechanisms which trigger an Active Galactic Nuclei (AGN or accreting supermassive black hole) and the role of these AGN in galaxy evolution, specifically in regulating or quenching star formation in galaxies, is a highly debated area of study. Theoretically, it is expected that mergers of galaxies should lead to the triggering of an AGN. In fact, this triggering is required by simulations to reproduce the observed properties of galaxies. Unfortunately, confirming that mergers trigger AGN is observationally challenging. The large observed variation in the frequency of AGN in different merger phases (wise/close pairs, post-mergers) are due to a number of factors including obscuration, time delays, AGN luminosities and AGN lifetimes. The overall interdependence of AGN luminosities and lifetimes impacts any correlation that should be seen between merger signatures and AGN frequency. Here I present a volume limited catalog of visually identified close pairs and merger remnants from the Sloan Digital Sky Survey (SDSS). Using this sample, I will present results based on an ongoing NASA Chandra and related NSF project to constrain the AGN frequency and multi-wavelength properties of systems whose merger signature lifetimes are theoretically expected to be similar to low luminosity AGN lifetimes.  I will describe the role of the SDSS MaNGA survey in characterizing the galaxy properties of these low luminosity AGN and the cold gas outflows from these systems. Time permitting, I will also describe a recent project to constrain the dual AGN fraction in a complete sample of dual galactic nuclei with separations between 1 and 10 kpc.