No new cosmological concordance with massive sterile neutrinos

TL;DR

This paper critically examines claims that massive sterile neutrinos could reconcile various cosmological observations, demonstrating that the supposed concordance is due to conflicting datasets and that standard models are statistically preferred.

Contribution

It provides a comprehensive analysis showing that the inclusion of sterile neutrinos does not improve cosmological fits and that current data strongly favor the minimal ΛCDM model.

Findings

The apparent concordance is due to dataset tensions.

Standard ΛCDM is strongly favored over neutrino extensions.

Upper limits on neutrino masses are approximately 0.3 eV at 95% CL.

Abstract

It has been claimed recently that massive sterile neutrinos could bring about a new concordance between observations of the cosmic microwave background (CMB), the large-scale structure (LSS) of the Universe, and local measurements of the Hubble constant, $H_0$. We demonstrate that this apparent concordance results from combining datasets which are in significant tension, even within this extended model, possibly indicating remaining systematic biases in the measurements. We further show that this tension remains when the cosmological model is further extended to include significant tensor modes, as suggested by the recent BICEP2 results. Using the Bayesian evidence, we show that the minimal $\Lambda$CDM model is strongly favoured over its neutrino extensions by various combinations of datasets. Robust data combinations yield stringent limits of $\sum m_\nu\lesssim0.3$ eV and $m_{\nu,{\rm sterile}}^{\rm eff} \lesssim 0.3$ eV at $95\%$ CL for the sum of active and sterile neutrinos, respectively.