Sommerfeld-Enhanced Annihilation in Dark Matter Substructure: Consequences for Constraints on Cosmic-Ray Excesses

Understand

In models of dark matter (DM) with Sommerfeld-enhanced annihilation, where the annihilation rate scales as the inverse velocity, N-body simulations of DM structure formation suggest that the local annihilation signal may be dominated by small, dense, cold subhalos.

• This contrasts with the usual assumption of a signal originating from the smooth DM halo, with much higher velocity dispersion.
• Accounting for local substructure modifies the parameter space for which Sommerfeld-enhanced annihilating DM can explain the PAMELA and Fermi excesses.
• Limits from the inner galaxy and the cosmic microwave background are weakened, without introducing new tension with substructure-dependent limits, such as from dwarf galaxies or isotropic gamma-ray studies.