Emulating the CFHTLenS Weak Lensing data: Cosmological Constraints from moments and Minkowski functionals

Abstract

Weak gravitational lensing is a powerful cosmological probe, with non--Gaussian features potentially containing the majority of the information. We examine constraints on the parameter triplet $(Ω_m,w,σ_8)$ from non-Gaussian features of the weak lensing convergence field, including a set of moments (up to $4^{\rm th}$ order) and Minkowski functionals, using publicly available data from the 154deg$^2$ CFHTLenS survey. We utilize a suite of ray--tracing N-body simulations spanning 91 points in $(Ω_m,w,σ_8)$ parameter space, replicating the galaxy sky positions, redshifts and shape noise in the CFHTLenS catalogs. We then build an emulator that interpolates the simulated descriptors as a function of $(Ω_m,w,σ_8)$, and use it to compute the likelihood function and parameter constraints. We employ a principal component analysis to reduce dimensionality and to help stabilize the constraints with respect to the number of bins used to construct each statistic. Using the full set of statistics, we find $Σ_8\equivσ_8(Ω_m/0.27)^{0.55}=0.75\pm0.04$ (68% C.L.), in agreement with previous values. We find that constraints on the $(Ω_m,σ_8)$ doublet from the Minkowski functionals suffer a strong bias. However, high-order moments break the $(Ω_m,σ_8)$ degeneracy and provide a tight constraint on these parameters with no apparent bias. The main contribution comes from quartic moments of derivatives.

17 pages, 10 figures, 4 tables