Institute of Astronomy

First Quasars

Observations of nearby galaxies and high redshift quasars suggest that black holes are present in the majority of galaxies. The Sloan Digital Sky Survey ( and the UKIDSS and VISTA surveys have found numerous high-redshift QSOs harbouring  black holes with masses in excess of a billion solar masses  at a  time when the Universe was less than 10% of it's current age. The fact that such massive black holes have managed to grow in less than a Gyr of cosmic time provides a significant challenge for theoretical models of the formation and growth of supermassive black holes.

Researchers at the IoA are performing state-of-the-art numerical simulations which follow self-consistently the growth of black holes from very early times to the present day. With these simulations, it is possible to study how black holes evolve with cosmic time, how their evolution depends on the large scale environment and how they affect their host galaxies. These simulations reproduce the brightest observed quasars at high redshifts in a full cosmological setting. They also give insight into why the most massive black holes grow "fastest", and why their mass tracks the growing stellar mass of the host galaxy. With these simulations we further investigate what role the spin of the black hole plays for their assembly.

Figure credits: Debora Sijacki; the simulations were carried out at the  Darwin high-performance compuer  in Cambridge with the massively parallel TREESPH code GADGET-3