Cosmology and galaxy evolution in the outskirts of galaxy clusters

Galaxy clusters are some of the most extreme objects in the Universe: huge haloes of dark matter, filled with hot intracluster gas, that are able to shape the lives of galaxies that reside within them. While the central regions of clusters are the most extreme, the quieter outskirts of clusters also hold a huge amount of information, much of which can be extracted with the aid of cosmological simulations. In this talk, I will show how simulations can be combined with observable properties of galaxy clusters to make inferences in two different areas of cosmology and astrophysics. Firstly, I will show how we can predict the frequency of backsplash galaxies -- galaxies that have previously passed through a cluster but now reside in its outskirts -- to better understand the dependence of galaxy evolution on cosmic environment. I will then show how we can use measurements of the density profiles of clusters to constrain cosmological parameters, and break existing degeneracies between these parameters.