The puzzle of galaxy and black hole co-evolution

rachel somerville / Rutgers

It is now widely believed that all spheroid-dominated galaxies harbor supermassive black holes in their nuclei, and that the mass of the black hole is strongly correlated with galaxy properties such as spheroid mass or luminosity. In addition, the evolution of the global star formation rate density over cosmic time seems to closely trace that of the global black hole accretion rate, suggesting that galaxies and their black holes grew together. However, in individual objects, star formation and black hole growth often appear to be uncorrelated. Moreover, many questions remain about the origin and evolution of supermassive black holes in galaxies, for example: what are the masses and physical origin of the first seed blackholes? How is black hole activity triggered and regulated? How does the energy released by accreting black holes shape their host galaxies? I will address these questions by confronting theoretical models that attempt to track the intertwined growth of galaxies and their black holes in a cosmological context with recent observations from multi-wavelength surveys.