The tidal evolution of dark galactic substructures

In this thesis we study the tidal evolution of dark matter subhaloes. We first look at reproducing the work of van den Bosch and Ogiya (2018), who suggested that modern cosmological simulations still suffer from excessive disruption of subhaloes due to gravitational tides. We were able to reproduce the results qualitatively, but not exactly, and found that our subhaloes were slightly more robust and resistant to disruption. We examine substructures in state-of-the-art cosmological simulations. We develop a technique to study substructures of a Milky Way-like halo from the Aquarius project (Springel et al., 2008) using the HEX technique (Lowing et al., 2011). HEX allows us to realistically model the potential of a halo in a computationally efficient fashion, which means that it is possible to run a large number of simulations of individual subhaloes. We find that the softening length does not seem to have a significant effect on the survival of substructure in realistic conditions. We find that with sufficient resolution, subhaloes which were lost in the original simulation do survive until the end. However, these subhaloes are relatively rare. We thus confirm that while there is artificial disruption, this does not appear to affect the substructure population as a whole in a realistic simulation.