The Co-evolution of Galaxies, Black Holes, and AGN in a Hierarchical   Universe
  The observational link between Supermassive Black Holes (SMBH) and galaxies at low redshift seems to be very tight, and statistically the global evolution of star formation activity and BH accretion activity also seem to trace each other closely. However, pinning down the co-evolution of galaxies and BH on an object-by-object basis remains elusive. I present results from new models for the joint evolution of galaxies, SMBH, and AGN, which may be able to help resolve some of the observational puzzles. A unique aspect of these models is our treatment of self-regulated BH growth based on hydrodynamic simulations of galaxy-galaxy mergers. Although these models do quite well at reproducing the observed evolution of galaxies, they do not reproduce the observed history of BH accretion, predicting too much early accretion and not enough at late times. I suggest two possible resolutions to this problem. 
Rachel S. Somerville