Neutrino masses and cosmic radiation density: combined analysis

Abstract

We determine the range of neutrino masses and cosmic radiation content allowed by the most recentCMB and large-scale structure data. In contrast to other recent works, we vary these parameterssimultaneously and provide likelihood contours in the two-dimensional parameter space ofNeff, the usual effective number of neutrino species measuring the radiation density, and ∑ mν. The allowed range of ∑ mν has shrunk significantly compared to previous studies. The previous degeneracy betweenthese parameters has disappeared, largely thanks to the baryon acoustic oscillation data.The likelihood contours differ significantly if ∑ mν resides in a single species instead of the standard case of being equally distributed amongall flavours. For ∑ mν = 0 we find 2.7 < Neff < 4.6 at 95% CL while ∑ mν < 0.62 eV at 95% CL for the standard radiation content.