The Milky Way mass function as a probe of dark matter models

ABSTRACT: Predictions for the properties of the Milky Way (MW) satellite galaxies are crucial tests for competing dark matter models. Deviations from the cold and collisionless picture of dark matter, such as free-streaming, dark acoustic oscillations, and self-interactions between dark matter particles, modify predictions for the number of MW satellite galaxies and/or for their densities. Calculating accurate predictions is complicated by the large array of factors relevant to satellite formation and processing, including the stochasticity of MW halo formation, the difficulties in modelling satellite stripping with limited resolution, and for contraction of the host halo through cooling baryons, to name but a few. In this talk I will use the COCO N-body simulations of MWanalogue systems to make estimates for the MW satellite population properties in three models: cold dark matter (CDM), a warm dark matter model (WDM) with a thermal relic mass of 3.3keV, and a self-interacting dark matter model (SIDM) that enables gravothermal collapse. I will use these models to predict the range of viable subhalo hosts for ~33 observed MW satellites, and then discuss how future observations will enable us to ascertain which model best describes the properties of dark matter.