Constraints on a nonthermal history from Galactic dark matter spikes

In this paper we examine whether indirect detection constraints on dark matter associated with a nonthermal history may be significantly improved when accounting for the presence of Galactic substructure in the form of dark matter spikes. We find that significant constraints may be derived from the nonobservation of an excess of diffuse gamma rays and from the properties of bright gamma-ray point sources observed by the Fermi Gamma-Ray Space Telescope, but these constraints depend sensitively on the details of the formation of the first stars and their subsequent black hole remnants. However, we also find that, especially if WIMPs annihilate primarily to quarks or gauge bosons, it is possible to extract meaningful and conservative bounds on the annihilation cross section.