Is cosmology compatible with sterile neutrinos?

By combining data from cosmic microwave background experiments (including the recent WMAP third year results), large scale structure, and Lyman-alpha forest observations, we constrain the hypothesis of a fourth, sterile, massive neutrino. For the 3 massless+1 massive neutrino case, we bound the mass of the sterile neutrino to m(s) 1 or < 0.05 eV, the cosmological energy density in sterile neutrinos is always constrained to be omega(nu)< 0.003 at 95% C.L., but for a mass of similar to 0.25 eV, omega(nu) can be as large as 0.01