Gas-rich dwarf galaxies as a new probe of dark matter interactions with ordinary matter

We use observations of gas-rich dwarf galaxies to derive constraints on dark matter scattering with ordinary matter. We require that heating/cooling due to DM interacting with gas in the Leo T dwarf galaxy not exceed the ultra-low radiative cooling rate of the gas. This enables us to set $(i)$ stronger bounds than all the previous literature on ultra-light hidden photon DM for nearly all of the mass range ${10}^{-23}\lesssim m_{\mathrm{D}\mathrm{M}}\lesssim {10}^{-10}$ eV, $(ii)$ limits on sub-GeV millicharged DM which add to the constraints on the recent EDGES 21cm absorption anomaly, and $(iii)$ constraints on DM-baryon interactions directly at low relative velocities $v_{\mathrm{r}\mathrm{e}\mathrm{l}}\sim 17$ km/s. Our study opens a new direction at using observations of gas-rich dwarf galaxies from previous, current and upcoming optical and 21cm surveys to probe physics beyond the standard model.