Velocity-dependent annihilation radiation from dark matter subhalos in
  cosmological simulations
  We use the suite of Milky Way-like galaxies in the Auriga simulations to
determine the contribution to annihilation radiation from dark matter subhalos
in three velocity-dependent dark matter annihilation models: Sommerfeld,
p-wave, and d-wave models. We compare these to the corresponding distribution
in the velocity-independent s-wave annihilation model. For both the
hydrodynamical and dark-matter-only simulations, only in the case of the
Sommerfeld-enhanced annihilation does the total annihilation flux from subhalos
exceed the total annihilation flux from the smooth halo component within the
virial radius of the halo. Progressing from Sommerfeld to the s, p, and d-wave
models, the contribution from the smooth component of the halo becomes more
dominant, implying that for the p-wave and d-wave models the smooth component
is by far the dominant contribution to the radiation. Comparing to the Galactic
center excess observed by Fermi-LAT, for all simulated halos the emission is
dominated by the smooth halo contribution. However, it is possible that for
Sommerfeld models, extrapolation down to mass scales below the current
resolution limit of the simulation would imply a non-negligible contribution to
the gamma-ray emission from the Galactic Center region.
