The first quasars and super-massive black holes

Quasars, which are powered by material falling into super-massive black holes, have been discovered when the Universe was just 5% of its current age (of 13.8 billion years). It is generally accepted that these black holes have masses in the range 10^9-10^10 Solar masses despite the fact that there is no known way to form and grow such objects in the available cosmological time.

The first part of this project is to use the results from surveys of distant quasars to determine their population and, in particular, how it is evolving with cosmic time. The observed numbers/properties of high-redshift quasars will be combined with other constraints on the super-massive black hole population, using Bayesian inference to combine the available information.

The second part of this project concerns the black holes themselves: it is very difficult to explain the formation of black holes of > 10^9 Solar masses in less than a billion years, but another possibility is that they are not actually so massive - their mass estimates come from extrapolating an imperfect empirical correlation established from a different population of quasars which, typically, have much lower mass black holes, and the current approaches to this problem tend to ignore the various significant sources of uncertainty; the approach here will be to go back to the original measurements and then use a hierarchical Bayesian model to link the black hole estimates to the actual astronomical observations.