The first quasars and super-massive black holes

类星体是环绕在星系中心的超大质量黑洞周围的发光气体圆盘，其亮度可能是其宿主星系的数百倍，而最亮的类星体是宇宙中最强大的非瞬变天体。类星体在宇宙只有现在年龄(138亿年)的5%时被发现，是追踪第一批超大质量黑洞形成的唯一途径。这个项目的第一部分将是利用对遥远类星体的调查结果来确定它们作为一个群体的性质，特别是它是如何随着宇宙时间演变的。这将涉及建模和贝叶斯推理的组合，以结合非常不同的样本的结果，从而有助于未来旨在推动更远距离的调查的设计。这个项目的第二部分涉及黑洞本身：很难解释在不到10亿年的时间里形成10^9个太阳质量的黑洞，但另一种可能性是它们实际上没有那么大的质量-它们的质量估计来自于外推一个不完美的经验关联式，该关联式建立在不同的类星体群中，通常类星体的质量要低得多，而目前解决这个问题的方法往往忽略了各种不确定因素。在这个项目中，我们将回到原始数据，建立关于第一个超大质量黑洞和类星体及其形成机制的真正可以说的东西。

A quasar, the glowing disk of gas around the super-massive black hole at the centre of a galaxy, can be hundreds of times more luminous than its host galaxy, and the brightest quasars are the most powerful non-transient objects in the Universe. Quasars have been discovered when the Universe was just 5% of its current age (of 13.8 billion years) and represent the only way to trace the formation of the first super-massive black holes. The first part of this project would be to use the results from surveys of distant quasars to determine their properties as a population and, in particular, how it is evolving with cosmic time. This will involve a combination of modelling and Bayesian inference to combine the results of very different samples, hence aiding the design of future surveys that aim to push to even greater distances. 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 sources of uncertainty. In this project we will go back to the original data and establish what can really be said about the first super-massive black holes and quasars and their formation mechanisms.