The relationship between black hole mass and galaxy properties: clues to the physics behind quiescence

Evidence from across the electromagnetic spectrum supports the theory that black hole (BH) feedback causes quiescence in massive galaxies. However, the form of this feedback and how it operates remains uncertain. I will describe results from a sample of 91 galaxies with dynamical BH masses and show that the BH-stellar mass relation has significant scatter which correlates strongly with star formation activity. In fact, for this diverse sample ranging from massive ellipticals to isolated spirals, the specific star formation rate is a smoothly decreasing function of the BH-stellar mass ratio. These results present a powerful diagnostic with which to test BH feedback's effects on star formation in the latest galaxy formation models. I will show how the relationship between BH mass, stellar mass, and star formation rate encodes information on the physics of quiescence in simulations such as IllustrisTNG, EAGLE, and L-Galaxies, thereby allowing a novel interpretation of the observations.