Flickering black holes

Quasars are the most luminous objects in the Universe, powered by accretion onto supermassive black holes. A key characteristic of quasars is their extreme variability, which provides a means of identifying these rare objects (given data of sufficient quality). The aim of this project is to identify quasars in a unique patch of sky (the Ultra Deep Survey), using very deep infrared imaging taken over an unprecedented baseline of 10 years. This would be the first study of its kind, which will provide a new and entirely independent census of quasar activity in the distant Universe. We expect to identify several thousand new quasars, allowing us to measure the growth of black holes at early times. By probing physical scales that are unresolvable by other means, the light curves will also provide new tests for models of quasar fuelling and accretion. As a bonus, we will also identify supernovae among the ~250,000 normal galaxies in the field, to provide a new statistical study of the prevalence of supernova activity in distant galaxies.