Dark Matter Subhalo Evaporation by Coulomb-like Interaction with Galactic Gas

Coulomb-like interactions typically have a cross section that scales with relative particle velocity as σ=σ₀ v⁻⁴. The momentum transfer rate between a slightly charged dark matter and ionized particles increases significantly at low velocity, so that it produces prominent evaporation effects on small-sized dark matter overdensities, which is a non-negligible influence for the evolution of dark matter subhalos. We calculate the subhalos evaporation rate in the ionized galactic region and show that below the limits from current cosmic microwave background and baryon acoustic oscillation data, galactic ionized particles can effectively evaporate subhalos below 107.5 M_ at a kilo-parsec distance from the galactic center, which can potentially affect the subhalos distribution in the inner galaxy. We also show the evaporation limits in terms of the electron-recoil direct detection cross section, and show that the evaporation effects can readily extend to the sub-MeV range which is unconstrained in direct detection experiments.