Exploring resonantly produced mixed sterile neutrino dark matter models

Abstract: An unidentified 3.55 keV X-ray line in stacked spectra of galaxies and clusters raises the interesting possibility that it originates from the decay of sterile neutrino dark matter. In this work, we explore mixed sterile neutrino dark matter models that combine cold dark matter and warmer sterile neutrino dark matter produced through lepton number-driven active-to-sterile neutrino transformation. We analyze the sensitivity of the sterile neutrino spectra on active-sterile mixing and on initial neutrino lepton numbers. Furthermore, we assess the viability of these models with estimates of the number of subhalos formed as the host sites of satellite galaxies.