"Dark-ages reionization and galaxy formation simulation - II. Spin and concentration parameters for dark matter haloes during the epoch of reionization" - Angel et al. (2016)
The first paper by Paul Angel for his PhD as part of DRAGONS and it's enormous. A careful phenomenological study and characterisation of the structure of dark matter haloes in the early universe. In particular Paul focussed on the concentration of the dark matter haloes as measured by fitting the halo with the NFW and Einasto profiles. At the current age of the universe works such as Duffy et al. (2008) show small mass haloes are typical denser (that is more concentrated) that more massive ones. This is because smaller objects form earlier than large objects in our hierarchical universe, earlier times in an expanding universe implies that it was overall smaller and hence denser as are then the objects that form. Paul discovered that the universe in DRAGONS is so young that essentially everything is forming at nearly the same time and hence density so the concentration-mass relation is flat!