Probing non-thermal light DM with structure formation and N _eff

Abstract In many models of dark matter (DM), several production mechanisms contribute to its final abundance, often leading a non-thermal momentum distribution. This makes it more difficult assess whether such model is consistent with structure formation observations. We simulate the power spectrum for DM scenarios characterized by at least two temperatures and derive suppression structures small scales expected number Milky Way dwarf galaxies from it. This, together known bound on relativistic particle species, N eff , allows us obtain constraints parameter space non-thermally produced DM. propose simple parametrization distributions present fitting procedure that can be used adapt our results other models.