Closing in on resonantly produced sterile neutrino dark matter

We perform an exhaustive scan of the allowed resonant production regime for sterile neutrino dark matter in order to improve constraints for dark matter structures which arise from the nonthermal sterile neutrino energy spectra. Small-scale structure constraints are particularly sensitive to large lepton asymmetries/small mixing angles which result in relatively warmer sterile neutrino momentum distributions. We revisit Milky Way galaxy subhalo count constraints and combine them with recent searches for x-ray emission from sterile neutrino decays. Together, they rule out models outside the mass range 7. 0 keVmₒ36 keV and lepton asymmetries smaller than 1510^-6 per unit entropy density at 95% confidence interval or greater. We also find that, while a portion of the parameter space remains unconstrained, the combination of subhalo counts and x-ray data indicates the candidate 3. 55 keV x-ray line signal potentially originating from a 7. 1 keV sterile neutrino decay to be disfavored at 93% confidence interval.