The Duty Cycle and Variability of Active Galactic Nuclei during Galaxy Quenching

The impact of AGN feedback on galaxies is difficult to assess due to the variability of AGN, with complete duty cycles more rapid than the timescales on which we observe evolutionary trends in galaxies. However, this variability also offers opportunities to measure the duty cycle of AGN activity, particularly in galaxies undergoing quenching. I will present results using AGN variability on a range of timescales in recently-quenched, post-starburst galaxies, with implications for how AGN feedback may act during this phase. I will discuss radio variability on decades-long timescales indicative of newly-launched outflows, as well as extended emission line regions that trace AGN activity on timescales of 10,000-100,000 years. With these variability tracers, we see evidence for AGN activity that is relatively weak and intermittent, but nonetheless contains enough energy to suppress star formation, drive the low velocity outflows seen in molecular gas, and remove molecular gas in quenching galaxies.