Non-Gaussianity in CMB lensing from full-sky simulations

TL;DR

This paper investigates the non-Gaussian features of CMB lensing convergence maps through full-sky simulations, demonstrating their potential to improve cosmological parameter constraints.

Contribution

It introduces a comprehensive simulation pipeline combining N-body and Gaussian fields, quantifies non-Gaussianity, and shows its utility in enhancing cosmological parameter estimation.

Findings

Non-Gaussianity can improve constraints on cosmological parameters.

Simulation code is publicly available.

Combining Gaussian and non-Gaussian info yields a few percent better constraints.

Abstract

The lensing convergence field describing the weak lensing effect of the Cosmic Microwave Background (CMB) radiation is expected to be subject to mild deviations from Gaussianity. We perform a suite of full-sky lensing simulations using ray tracing through multiple lens planes - generated by combining $N$-body simulations on smaller scales and low-to-intermediate redshifts with realisations of Gaussian random fields on large scales and at high redshifts. We quantify the non-Gaussianity of the resulting convergence fields in terms of a set of skewness and kurtosis parameters and show that the non-Gaussian information in these maps can be used to constrain cosmological parameters such as the cold dark matter density $\Omega_\mathrm{c} h^2$ or the amplitude of primordial curvature perturbations $A_\mathrm{s}$. We forecast that for future CMB lensing observations, combining the non-Gaussian parameters with the Gaussian information can increase constraining power on $(\Omega_\mathrm{c} h^2, A_\mathrm{s})$ by a few per cent compared to constraints from Gaussian observables alone. We make the simulation code for the full-sky lensing simulation available for download from GitHub.