Searching for velocity-dependent dark matter annihilation signals from extragalactic halos

I consider gamma-ray signals of dark matter annihilation in extragalactic halos in the case where dark matter annihilates from a p-wave or d-wave state. In these cases, signals from extragalactic halos are enhanced relative to other targets, because the typical relative speed of the dark matter is larger in extragalactic halos. I perform a mock data analysis of gamma rays produced by dark matter annihilation in halos detected by the Sloan Digital Sky Survey. I find that searches of extragalactic halos with the current Fermi exposure can produce evidence for dark matter annihilation, though it is difficult to distinguish the p-wave and d-wave scenarios. With a factor 10x larger exposure, though, discrimination of the velocity-dependence is possible.