Constraining p-wave Dark Matter Annihilation with Gamma-ray Observations of M87

We investigate the gammay-ray signal from dark matter annihilating in a dark matter spike surrounding the supermassive black hole at the center of M87. Owing to the large mass of the black hole, and the resulting large velocity dispersion for the dark matter particles in the spike, it is possible that Fermi-LAT and MAGIC data tightly constrain p-wave annihilation, and far more stringently so than observations of gamma rays from dwarf spheroidal galaxies. Indeed, for optimistic choices of the spike parameters, gamma-ray data would exclude thermal p-wave dark matter models for dark matter masses less than around 10 TeV. But there is significant uncertainty in the properties and parameters of the spike, and for less optimistic scenarios, thermal dark matter candidates could even be completely unconstrained.