Title: Dark matter halo response to baryons
Abstract: While dark matter halo density profiles in dark-matter-only simulations are well described by NFW cusps, observations infer shallower cores and the introduction of baryons in the simulations results in the formation of cores in a specific mass range. This behaviour can be interpreted in terms of a competition between outflows induced by feedback and the confinement imposed by halo gravity. I will first present a parametrization of dark matter halo density profiles with variable inner slope and concentration that enables to describe the variety of halo responses and has analytic expressions for the gravitational potential, velocity dispersion, and lensing properties. This parametrization provides a useful tool to study the evolution of dark matter haloes, to model rotation curves of galaxies and gravitational lenses, and to implement in semi-analytical models of galaxy evolution. I will then present two simple theoretical models describing core formation in dark matter haloes. In the first one, sudden bulk outflows induced by stellar feedback reorganise the halo mass distribution while it relaxes to a new equilibrium. In the second one, small stochastic density fluctuations induce kicks to collisionless particles that progressively deviate them from their orbits. Both models are tested against numerical simulations and provide a simple understanding of the transition from cusps to cores by feedback-driven outflows.