A survey of galaxies using the European Space Agency (ESA)’s Herschel Space Observatory has shown that only the most powerful black holes in the early Universe were able to quench the formation of stars in their host galaxies. This finding is an important contribution to our understanding of one of the most hotly debated phases of galaxy evolution.
The first galaxies in the history of the Universe started to form a few hundred million years after the Big Bang. At this very early epoch in cosmic history, galaxies were quite different to those that are now observed in the local Universe. Early galaxies produced stars at tremendous rates and the supermassive black holes residing at their centres were exceptionally active in accreting the surrounding matter.
Galaxy surveys indicate that both star formation and black hole accretion were most intense when the Universe was only a few billion years old, and that this later declined to the moderate rates observed in local galaxies.