Astrophysical Probes of the Particle Nature of a Secluded Dark Sector

The particle identity of dark matter is poorly understood and constraints on its possible non-gravitational interactions with the Standard Model have become increasingly stringent over the last decade. With the lack of convincing experimental evidence for such interactions, the possibility that its particle nature can only be probed via its gravitational interactions seems like a realistic scenario, which must be addressed. Theoretical arguments, as well as some observational data, point towards the possibility that dark matter could have non-trivial internal dynamics. If this turns out to be true, galactic and sub-galactic astrophysical structure provides crucial probes into the microscopic physics of the dark sector and its dark matter content. For example, dark matter with sizable self interactions, dissipation, or internal degrees of freedom, can leave distinctive signatures on the properties of galaxies and their satellites. I will discuss how to probe the parameter space of self-interacting dark matter models using dwarf galaxy properties and how to extend this formalism to other dark sector models, by using statistical properties of galaxies in realistic astrophysical environments.