A new life for sterile neutrinos: resolving inconsistencies using hot dark matter

Within the standard ACDM model of cosmology, the recent Planck measurements have shown discrepancies with other observations, e.g., measurements of the current expansion rate H-0, the galaxy shear power spectrum and counts of galaxy clusters. We show that if ACDM is extended by a hot dark matter component, which could be interpreted as a sterile neutrino, the data sets can be combined consistently. A combination of Planck data, WMAP-9 polarisation data, measurements of the BAO scale, the HST measurement of H-0, Planck galaxy cluster counts and galaxy shear data from the CFHTLens survey yields Delta N-eff = 0.61 +/- 0.30 and m(s)(eff) = (0.41 +/- 0.13) eV at la. The former is driven mainly by the large H-0 of the HST measurement, while the latter is driven by cluster data. CFHTLens galaxy shear data prefer Delta N-eff > 0 and a non-zero mass. Taken together, we find hints for the presence of a hot dark matter component at 3 sigma. A sterile neutrino motivated by the reactor and gallium anomalies appears rejected at even higher significance and an accelerator anomaly sterile neutrino is found in tension at 2 sigma.