Event Details

Tracking the incidence of AGN across the galaxy population

Determining whether certain conditions within a galaxy enhance or reduce the level of central black hole growth is challenging. Variability in AGN activity on short timescales compared to changes across the host galaxy can wash out underlying correlations between galaxy and AGN properties, resulting in a complex and biased observational picture. I will present work that addresses these issues, starting from near-infrared selected samples of galaxies and directly measuring the distribution of AGN accretion rates within such samples using deep Chandra X-ray data. We thus trace how the incidence of AGN changes as a function of stellar mass and star formation rate over a broad range in cosmic time (z~0.1-4). We first consider star-forming galaxies that lie along the main sequence and show that the incidence of AGN (quantified in terms of the AGN fraction or average specific accretion rates) is correlated with the SFR, indicating that AGN activity is primarily related to the amount of cold gas in a galaxy. We also consider galaxies with a broader range of SFRs relative to the main sequence, finding evidence for an enhanced incidence of AGN and indicating that a broader range of mechanisms are responsible for the triggering and fuelling of AGN across the galaxy population.Abstract: