Velocity-dependent J-factors for annihilation radiation from cosmological simulations

We determine the dark matter pair-wise relative velocity distribution in a set of Milky Way-like halos Auriga and APOSTLE simulations. Focusing on smooth halo component, is well-described by Maxwell-Boltzmann over nearly all radii halo. explore implications for velocity-dependent annihilation, focusing four models which scale as different powers velocity: Sommerfeld, s-wave, p-wave, d-wave models. show that J-factors moments distribution, halo-to-halo scatter largest d-wave, smallest Sommerfeld The J-factor strongly correlated with density halo, very weakly dispersion. This implies if Way can be robustly determined, one accurately predict annihilation signal, without need to identify Galaxy.