Cosmological singlet diagnostics of neutrinophilic dark matter

The standard model (SM) of particle physics is extended by adding a fundemantal dark sector containing a dark matter singlet, which is coupled to the visible sector via a gauge invariant Yukawa portal and a sterile neutrino bridge. The cases of weakly interacting dark matter particles and feebly interacting ones are both considered. Even after the Yukawa portal is closed, the sterile neutrino bridge keeps the communication between the dark and visible sectors open, allowing for a prolonged contact between dark matter and standard model neutrinos. Such a dark sector is UV-complete and satisifies all particle physics and cosmological constraints. In particular, it leads to an acceptable formation of dark matter substructures with reasonable mass scales for the typical first protohalos.