Dwarf Galaxy Constraints on Self-Interacting Dark Matter

We examine the transition from the primordial, cuspy NFW halos of dwarf galaxies found in simulations to the observed density profiles of today's Milky Way dwarf galaxies in the context of self-interacting dark matter (SIDM) models. Based on the requirement that the elastic scattering of the SIDM removes the cusp mass of each dwarf galaxy, we find $\sigma $/m \textless 0.06 cm$^{\mathrm{2}}$/g, even in the least restrictive case (Leo II). These constraints rule out the range of values favored to remove the cusps of larger galaxies in recent simulations: 0.1 cm$^{\mathrm{2}}$/g \textless $\sigma $/m \textless 1 cm$^{\mathrm{2}}$/g.