Black-hole-regulated star formation in massive galaxies

Super-massive black holes, with masses larger than a million times that of the Sun, appear to inhabit the centers of all massive galaxies. Cosmologically-motivated theories of galaxy formation need feedback from these super-massive black holes to regulate star formation. In the absence of such feedback, state-of-the-art numerical simulations dramatically fail to reproduce the number density and properties of massive galaxies in the local Universe. However, there is no observational evidence of this strongly coupled co-evolution between super-massive black holes and star formation, impeding our understanding of baryonic processes within galaxies. Here we show that the star formation histories (SFHs) of nearby massive galaxies, as measured from their integrated optical spectra, depend on the mass of the central super-massive black hole. Our results suggest that black hole mass growth scales with gas cooling rate in the early Universe. The subsequent quenching of star formation takes place earlier and more efficiently in galaxies hosting more massive central black holes. The observed relation between black hole mass and star formation efficiency applies to all generations of stars formed throughout a galaxy's life, revealing a continuous interplay between black hole activity and baryon cooling.
Comment: Published in Nature, 1 January 2018