Research

Galaxies are great; full of complexity, rich in variety and very pretty to look at! One way or another all my research is related to galaxies and more specifically to disc galaxies (like our own Milky Way and its nearest neighbour, Andromeda).

Galaxies are pretty tricky to study, astrophysics is unlike most other scientific pursuits in that you cannot actually do experiments! All you can do is take a look at each galaxy from a single perspective and you certainly cannot see how they evolve because the timescales are simply too long.

Fortunately we think we know a few things about what goes into making a galaxy. We know¹;

  • the laws of gravity
  • that gas emits and absorbs radiation
  • that stars form from dense regions of gas
  • stars output radiation, stellar winds and explode as supernovae
  • that they are composed of stars, gas (mostly hydrogen and helium) and an invisible kind of matter we call ‘dark matter’

By combining these processes we can create computer models of galaxy formation to see how these processes interact and conspire to create these spiral galaxies. I am interested in how the star forming regions of the galaxy come to be and how they are destroyed by the stars that they create and by the galactic environment itself. I run simulations like the one shown below and investigate the properties of these star forming regions.

Galaxies do not exist in complete isolation though and do occasionally interact with one another. In fact galaxies quite often accrete small satellites that form around them and these mergers and accretions have an effect on the galaxies. Some of my simulations include this effect of cosmology in which nearby galaxies can encounter one another, often with dramatic consequences as shown below.

The largest of these mergers can result in elliptical galaxies, but I am mostly interested in those that retain a disc/spiral shape. I investigate how elements heavier than helium are distributed within galaxies after they are formed by nuclear fusion within stars. Metallicity gradients across the galactic disc give us insight into the way that galaxies formed (the inner regions first, moving outwards) but can be disturbed when two galaxies merge with one another.

The internal chemical evolution of galaxies is another of my interests and I have developed the simulation code RAMSES into RAMSES-CH, so that the production of different elements is followed during my simulations. This code is being used to investigate chemical evolution in galaxies in a cosmological context.

These are just a few of the things that I spend my time investigating, details can be found in my publications.

Please feel free to use the movies and pictures on this page, but let me know and cite them appropriately (just my name will do!).

¹ For a certain value of “know”.