Dark Matters

If gravitationally bound structures grew from small fluctuations in the initial distribution, then the statistics of the initial fluctuation field may be used to estimate many properties of the evolved dark halo distribution. I only consider hierarchical clustering. That is, I assume that mergers are common and fragmentation is not; objects present at any given time were made by mergers of smaller objects that had formed still earlier. I describe current models of the evolved halo density profiles, the forest of merger history trees associated with dark halos, and how knowledge of this forest allows one to quantify the extent to which halos are biased tracers of the dark matter distribution. 1 Density profiles of dark matter halos Numerical simulations of hierarchical gravitational clustering show that, when expressed in units of the virial density and radius, the ensemble averaged density profiles of virialized dark matter halos show the following trends: on average, for a given ini..