Figure Rotation of Dark Halos in Cold Dark Matter Simulations

We have simulated structure formation on cosmological-scales using N-body simulations run in parallel at the University of KwaZulu-Natal and have used these simulations to investigate aspects of galaxy evolution. In particular, we focus on the rotation of dark matter halos identified in Cold Dark Matter (CDM) simulations. We have demonstrated that the mass function and spin distribution of our simulated halos are consistent with previous studies. After removing from our sample all halos that have either recently undergone major mergers, or contain a significant amount of substructure, approximately 75% of the remaining halos were found to undergo coherent rotation over periods of 3 Gyr. The pattern speeds were found to follow a log-normal distribution, with an average value of 0.13h radians Gyr^-1. The most rapidly rotating halo detected was found to have a pattern speed of 0.41h radians Gyr^-1. Many halos showed alignment between their rotation and minor axes. We found no correlation between halo properties, such as total mass, and the pattern speed. While the speeds observed were not sufficient to cause observed spiral structure, the rotation could be relevant for understanding other observations of galaxies.