Active galactic nuclei are powered by the in-fall of gas towards a black hole, and can be so luminous that
they may alter the evolution of the galaxies in which they reside. While all large galaxies host black holes,
only some galaxies host active galactic nuclei, so these mysterious objects must be triggered by brief or rare
circumstances. Models of active galactic nuclei predict how frequently they occur and where their host
galaxies should reside. We will test these predictions using large multi-wavelength astronomical surveys and
innovative techniques for measuring the faint emission from active galactic nuclei and the dark matter
masses of galaxies. This will allow us to determine the circumstances that trigger active galactic nuclei.