Gamma-ray signatures of annihilation to charged leptons in dark matter
  substructure
  Due to their higher concentrations and small internal velocities, Milky Way
subhalos can be at least as important as the smooth halo in accounting for the
GeV positron excess via dark matter annihilation. After showing how this can be
achieved in various scenarios, including in Sommerfeld models, we demonstrate
that, in this case, the diffuse inverse-Compton emission resulting from
electrons and positrons produced in substructure leads to a nearly-isotropic
signal close to the level of the isotropic GeV gamma-ray background seen by
Fermi. Moreover, we show that HESS cosmic-ray electron measurements can be used
to constrain multi-TeV internal bremsstrahlung gamma rays arising from
annihilation to charged leptons.
