  Previous fits of sterile neutrino dark matter models to cosmological data
assumed a peculiar production mechanism, which is not representative of the
best-motivated particle physics models given current data on neutrino
oscillations. These analyses ruled out sterile neutrino masses smaller than
8-10 keV. Here we focus on sterile neutrinos produced resonantly. We show that
their cosmological signature can be approximated by that of mixed Cold plus
Warm Dark Matter (CWDM). We use recent results on LambdaCWDM models to show
that for each mass greater than or equal to 2 keV, there exists at least one
model of sterile neutrino accounting for the totality of dark matter, and
consistent with Lyman-alpha and other cosmological data. Resonant production
occurs in the framework of the nuMSM (the extension of the Standard Model with
three right-handed neutrinos). The models we checked to be allowed correspond
to parameter values consistent with neutrino oscillation data, baryogenesis and
all other dark matter bounds.

High Energy Physics - Phenomenology;Astrophysics