Thursday, 1 May 2014

Satellites as Probes of Cosmology

One of the topics my collaborators and I are particularly interested in is understanding what satellite galaxies can tell us about galaxy formation and cosmology. I'm lucky enough to work with some excellent people who are experts in real observations of the satellite populations of the Milky Way and Andromeda galaxies, and the idea is that we can use simulations of galaxies and make synthetic observations of their satellites to help us make sense of the real observations, i.e. what are they really telling us about how the Universe works. 

If you look at this little movie showing the spatial distribution of stars in and around an isolated Milky Way type galaxy, you can see distinct clumps -- satellites -- as well as thread-like streams looping over the galaxy, the tell-tale signature that the galaxy is cannibalising its population of satellites. 

This process of galactic cannibalism is well know -- the figure on the right is an artist's impression of what is happening, and some spectacular evidence has been found in the Sloan Digital Sky Survey's Field of Streams. However, it's very nice to see it occurring in one of my cosmological galaxy formation simulations, which are of moderate resolution. This suggests that we can study ensembles of galaxies -- spanning a range of masses, environments and assembly histories in different dark matter models and for different galaxy formation prescriptions -- and explore parameter space in a much less computationally expensive way than I had initially anticipated. My collaborators here at UWA, over at U Sydney and at UAM in Spain have a big grant to study this problem over the next 3 years -- and so if you want to know what we are learning… watch this space!