Diffuse Gamma Ray Background from Annihilating Dark Matter in Density Spikes around Supermassive Black Holes

Dark matter annihilation is proportional to the square of the density and is especially efficient in places of highest concentration of dark matter, such as dark matter spikes. The spikes are formed as a result of contraction of the dark matter density profile caused by adiabatic growth of a supermassive black hole at the center of the dark matter halo or subhalo. We revisit the relation between the properties and mass functions of dark matter halos and spikes, and propose alternative models for the density spikes that can potentially contribute to the isotropic gamma-ray background.