Dark matter density profiles of halos in the Illustris Simulation

We conduct a detailed study of the evolution of dark matter density as a function of radius for the most massive galaxy halos in the Illustris Simulation. The dark matter density profiles of these clusters are fit using a generalized NFW function. With the tree structure of Illustris, each halo is traced back to its progenitor across many redshifts, gaining insights into the evolution of the profile parameters as a function of cosmic time and halo environment throughout the merger history. The power law value from the NFW function is plotted as a function of dark matter mass as well as dark matter percentage and compared to its progenitors, as is the total halo mass and dark matter percentage. We uncover correlations in the relationships among these parameters within individual halo tree histories. These correlations indicate that the process of hierarchical structure formation through mergers, while largely dependent on the initial conditions of each halo, does follow broader trends whose explanation we reserve for future work.