CFHTLenS: Cosmological constraints from a combination of cosmic shear two-point and three-point correlations

TL;DR

This paper measures second- and third-order weak-lensing statistics from CFHTLenS, combining them with CMB data to improve constraints on cosmological parameters, especially $\sigma_8$ and $\Omega_m$, and explores potential systematics and future challenges.

Contribution

It introduces the first measurement of third-order weak-lensing aperture-mass moments from CFHTLenS and demonstrates their utility in tightening cosmological constraints when combined with CMB data.

Findings

Third moment measured with 2σ significance.

Combined lensing and CMB data improve parameter constraints by up to 43%.

Including general triangle configurations yields tighter constraints.

Abstract

Higher-order, non-Gaussian aspects of the large-scale structure carry valuable information on structure formation and cosmology, which is complementary to second-order statistics. In this work we measure second- and third-order weak-lensing aperture-mass moments from CFHTLenS and combine those with CMB anisotropy probes. The third moment is measured with a significance of $2\sigma$. The combined constraint on $\Sigma_8 = \sigma_8 (\Omega_{\rm m}/0.27)^\alpha$ is improved by 10%, in comparison to the second-order only, and the allowed ranges for $\Omega_{\rm m}$ and $\sigma_8$ are substantially reduced. Including general triangles of the lensing bispectrum yields tighter constraints compared to probing mainly equilateral triangles. Second- and third-order CFHTLenS lensing measurements improve Planck CMB constraints on $\Omega_{\rm m}$ and $\sigma_8$ by 26% for flat $\Lambda$CDM. For a model with free curvature, the joint CFHTLenS-Planck result is $\Omega_{\rm m} = 0.28 \pm 0.02$ (68% confidence), which is an improvement of 43% compared to Planck alone. We test how our results are potentially subject to three astrophysical sources of contamination: source-lens clustering, the intrinsic alignment of galaxy shapes, and baryonic effects. We explore future limitations of the cosmological use of third-order weak lensing, such as the nonlinear model and the Gaussianity of the likelihood function.