Title: The study of Active Galactic Nuclei variability on multiple timescales
by Lia Sartori (ETH Zurich)
The study of Active Galactic Nuclei (AGN) variability on multiple timescales can provide important information about supermassive black hole accretion physics, as well as the black hole – host galaxy interaction and coevolution.
AGN variability on human timescales (days to decades) can be explored in large photometric surveys such as the Sloan Digital Sky Survey (SDSS), while galaxies with extended AGN photoionised emission line regions (~ 10 kpc scale) allow to trace AGN variability on ~ 10^4 yr timescales. On the other hand, recent studies suggest that AGN may flicker on and off hundreds or thousands times, with each burst lasting ~ 10^5 yr. As a consequence, AGN can continuously switch from very active phases with luminosity exceeding the one of the whole host galaxy (these are the so-called quasars) to very quite phases as it is the case for Sagittarius A*, the black hole in our own Milky Way.
After reviewing the basics of the AGN phenomenon, I’ll show how different samples of AGN can be used to study the different phases of the AGN lifecycle. In addition, I will present a new model which allows to link and study AGN variability on a wide range of timescales, from days to the age of the Universe.