I will present strong indirect evidence for the star formation in central galaxies being regulated by AGN feedback, most likely through the ‘radio-mode’. We analyse a population of over half a million central galaxies drawn from the SDSS. For all of these galaxies we derive photometric bulge + disk decompositions in each of the Sloan ugriz wavebands, and combine these to form stellar masses for the components. We find a much stronger dependence of the passive fraction on bulge mass than on total stellar mass, B/T morphology, disk mass, local galaxy density, or group halo mass (derived from an abundance matching technique). This suggests the process that quenches central galaxies is intimately connected to the process that builds up galactic bulges (Bluck et al. 2014). Moreover, recent work we have completed finds a stronger still dependence of the passive fraction on central velocity dispersion and inferred black hole mass (Bluck et al. in prep.). Crucially, our results indicate that to understand the end of star formation in galaxies, one must first look inward to the centre of galaxies (and indeed to their central black holes) before looking outward to the galaxy’s surrounding disk, dark matter halo, or local environment. I will conclude by discussing the implications of our findings for galaxy formation models.
Host: Paul Torrey