A search for sterile neutrinos with the latest cosmological observations

Understand

We report the result of a search for sterile neutrinos with the latest cosmological observations.

• Both cases of massless and massive sterile neutrinos are considered in the $\Lambda$CDM cosmology.
• The cosmological observations used in this work include the Planck 2015 temperature and polarization data, the baryon acoustic oscillation data, the Hubble constant direct measurement data, the Planck Sunyaev-Zeldovich cluster counts data, the Planck lensing data, and the cosmic shear data.
• We find that the current observational data give a hint of the existence of massless sterile neutrino (as dark radiation) at the 1.44$\sigma$ level, and the consideration of an extra massless sterile neutrino can indeed relieve the tension between observations and improve the cosmological fit.