Black hole dynamics and the origin of supermassive black holes

Almost every massive galaxy has a supermassive black hole in its centre, which grew from a small black hole as the Universe evolved. Such supermassive black holes do not only reside in galaxies, they are thought to significantly shape the evolution of their host galaxy and be one of the physical drivers behind the wide variety of galaxy shapes and sizes we see in the Universe today.

There is no known way to directly form a supermassive black hole at the masses they have today. Instead, supermassive black holes started their journey as much lighter black holes when the Universe was young. Such light black holes, which then grew into supermassive black holes, are called "seed black holes".

Seed black holes grew in mass through material that fell into the black hole, or through mergers with other black holes. To understand the tight link between galaxies and the supermassive black holes that we see today, we need to understand when and how seed black holes first formed and found their way into the centre of the galaxies in which we see supermassive black holes today.

It was long thought that each galaxy would easily acquire one such seed black hole when the galaxy was young but recent work has shown that the process is not trivial. Black holes in the early Universe often form far from the kind of galaxies where we see supermassive black holes today, or are very light when formed and easily ejected from galaxies, and the timescales for them to settle (back) into the centres of galaxies can be very long.

We do not yet have a good understanding of how seed black holes travel from their formation sites to galaxies, and whether they are able to remain in galaxies long enough to grow supermassive or whether they often get ejected again.

In this project, I will tackle the difficult challenge of how black holes in the early Universe move in and around galaxies, to understand when and how they first found their way into the galaxies where we see supermassive black holes today. To do so, I will combine powerful simulations with recent observations of the early Universe to study how a diverse population of black holes evolves in and around early galaxies.

In this way, I will pave the way towards understanding how galaxies first acquired their seed black holes, and when the coevolution between black holes and galaxies began.