Co-evolution of bulges and black holes

In the present-day universe, the global properties of bulges and early-type galaxies correlate with the mass of their central black holes, indicating a connection between galaxy evolution and nuclear activity. Understanding the origin of this relation is a major challenge for cosmological models. Using Keck spectra and HST images, we present direct measurements of the correlations between black hole mass and host spheroid luminosity and velocity dispersion at z=0.36, showing that the relations evolved significantly in the past 4 billion years. It appears that black holes of a few 10⁸ M_⊙ completed their growth before their host galaxies, and that the current scaling relations are only the final point of the co-evolution of galaxies and black holes.