Gas-rich dwarf galaxies as powerful dark matter detectors

Gas-rich dwarf galaxies located outside the virial radius of their host are relatively pristine systems and have ultra-low gas cooling rates. This makes them very sensitive to heat injection by non-standard dark matter (DM). I will show that by requiring the gas heating rate by DM to not exceed the cooling rate of gas in the Leo T dwarf galaxy, one gets strong constraints on popular DM models like millicharged DM, axion like particles (ALPs) and primordial black holes (PBHs). For dark photon DM and for DM decay models, Leo T gives stronger constraints than all the previous literature. I will therefore show that observations of gas-rich dwarfs like Leo T from current and upcoming 21cm and optical surveys (e.g., Rubin observatory, Roman telescope) open a new way of probing DM.