In light of the recent BICEP2 B-mode polarization detection , which implies a large inflationary tensor-to-scalar ratio r _ { 0.05 } = 0.2 ^ { +0.07 } _ { -0.05 } , we re-examine the evidence for an extra sterile massive neutrino , originally invoked to account for the tension between the cosmic microwave background ( CMB ) temperature power spectrum and local measurements of the expansion rate H _ { 0 } and cosmological structure .
With only the standard active neutrinos and power-law scalar spectra , this detection is in tension with the upper limit of r < 0.11 ( 95 % confidence ) from the lack of a corresponding low multipole excess in the temperature anisotropy from gravitational waves .
An extra sterile species with the same energy density as is needed to reconcile the CMB data with H _ { 0 } measurements can also alleviate this new tension .
By combining data from the Planck and ACT/SPT temperature spectra , WMAP9 polarization , H _ { 0 } , baryon acoustic oscillation and local cluster abundance measurements with BICEP2 data , we find the joint evidence for a sterile massive neutrino increases to \Delta N _ { eff } = 0.98 \pm 0.26 for the effective number and m _ { s } = 0.52 \pm 0.13 eV for the effective mass or 3.8 \sigma and 4 \sigma evidence respectively .
We caution the reader that these results correspond to a joint statistical evidence and , in addition , astrophysical systematic errors in the clusters and H _ { 0 } measurements , and small-scale CMB data could weaken our conclusions .