Creating Dark Matter Cosmological Simulations to Investigate the Cusp/Core Debate

Abstract

Simulations involving only dark matter predict central density profiles that are cusps: asymptotically peaked negative power-laws. However observational data shows that the dark matter distribution in smaller galaxies, such as dwarf galaxy satellites of the Milky Way, are not cusped. Instead, observations of the orbits of stars in dwarf galaxies indicate a relatively constant density dark matter profile in the central 2 kpc, implying considerably less matter in those regions than expected for a cuspy profile. Simulations have shown that highly dynamic motions of baryons such as those created from stellar feedback can gravitationally transfer energy to collisionless components, like dark matter, and move it to larger orbits. The net effect is to lower the central density and create a core. Here, we present the creation of a high-resolution zoom simulation involving only dark matter. The steps involved in the creation of initial conditions is described and can be easily extended to include baryonic matter. Simulation analysis shows high-resolution (M_DM ∼ 8 × 10^3 M_⊙) dwarf galaxies presenting cuspy density profiles. Future work recreating the presented simulation with the addition of baryonic matter and feedback can compare with the results presented here and further explore cusp vs core formation.