Dark Matter Halo Mass Function From HPC N-body Simulations

Dark matter (DM) dominates the matter in the Universe. Because of self-gravity, DM collapses and becomes clumpy, building the large-scale hierarchical structures. Baryons assemble within DM potential wells and form galaxies. Because we can not directly observe DM halos, numerical simulations is the only way one can study their dynamics and other properties. Using N-body simulations, we can obtain the Halo Mass Function (HMF), which provides the abundance of DM halos as a function of their mass. The HMF depends weakly on cosmological redshift and is one of the basic tools in modern cosmology. We use GIZMO --- a flexible, multi-method magneto-radiation-hydrodynamics code with self-gravity. It is designed to simultaneously capture advantages of both hydrodynamics via grid-based/adaptive mesh refinement (AMR) schemes and collisionless dynamics of stars and DM