Cosmic Discordance: Are Planck CMB and CFHTLenS weak lensing measurements out of tune?

TL;DR

This paper investigates the discrepancy between Planck CMB and CFHTLenS weak lensing measurements, finding significant tension that persists across various models and systematics, and explores potential resolutions including sterile neutrinos.

Contribution

The study provides a comprehensive, systematic analysis of CFHTLenS weak lensing data, extending previous work and highlighting the persistent tension with Planck CMB results, while updating cosmological fitting functions.

Findings

CFHTLenS and Planck+WP contours do not overlap in ΛCDM.

Adding sterile neutrinos can reconcile datasets by increasing effective neutrino number.

Discrepancy remains unresolved by neutrino mass or tensor modes alone.

Abstract

We examine the level of agreement between low redshift weak lensing data and the CMB using measurements from the CFHTLenS and Planck+WMAP polarization. We perform an independent analysis of the CFHTLenS six bin tomography results of Heymans et al. (2013). We extend their systematics treatment and find the cosmological constraints to be relatively robust to the choice of non-linear modeling, extension to the intrinsic alignment model and inclusion of baryons. We find that the 90% confidence contours of CFHTLenS and Planck+WP do not overlap even in the full 6-dimensional parameter space of $\Lambda$CDM, so the two datasets are discrepant. Allowing a massive active neutrino or tensor modes does not significantly resolve the disagreement in the full n-dimensional parameter space. Our results differ from some in the literature because we use the full tomographic information in the weak lensing data and marginalize over systematics. We note that adding a sterile neutrino to $\Lambda$CDM does bring the 8-dimensional 64% contours to overlap, mainly due to the extra effective number of neutrino species, which we find to be 0.84 $\pm$ 0.35 (68%) greater than standard on combining the datasets. We discuss why this is not a completely satisfactory resolution, leaving open the possibility of other new physics or observational systematics as contributing factors. We provide updated cosmology fitting functions for the CFHTLenS constraints and discuss the differences from ones used in the literature.