Modelling Accretion Disk Winds

All quasars are powered by the same central engine: a supermassive black hole that is surrounded and fed by a luminous accretion disk. Approximately 15% of all quasars exhibit clear evidence for powerful outflows driven from these disks, in the form of broad, blue-shifted absorption lines. However, these so-called "broad absorption line quasars" (BALQSOs) are just the tip of the iceberg: since disk-driven winds cannot be spherical, BALQSOs are just the sub-set of quasars viewed at a particularly favourable orientation. In reality, *all* quasars are likely to drive such winds. This is important, because these outflows provide a key feedback mechanism: they can remove significant amounts of mass, energy and angular momentum from the quasar and inject it into the surrounding (inter-)galactic medium. However, despite their importance, we know almost nothing about these accretion disk winds. For example, the geometry, kinematics, and even the basic driving mechanism responsible for launching them are still basically unknown.

The aim of this PhD project will be to remedy this situation by modelling the wind-formed features in the spectra of quasars. This work will be carried out in the context of an established collaboration (which includes two other PhD students and one postdoctoral fellow at Southampton) and will use an existing, state-of-the-art Monte Carlo radiative transfer code. The ultimate goal we are pursuing is to determine the fundamental parameters of quasar accretion disk winds and thus shed light on how they regulate the fueling of supermassive black holes and the feedback of energy into their environment. In addition, we aim to shed light on quasar unification: is it possible that *most* observational signatures we associate with (even non-BAL) quasars are actually shaped by disk winds?