Precision of diffuse 21-cm lensing

TL;DR

This paper investigates the fundamental limits of weak lensing maps of dark matter using diffuse 21-cm radiation from the pre-reionization epoch, highlighting the impact of non-Gaussianity and proposing improved estimators.

Contribution

It introduces shear and convergence-based estimators for 21-cm lensing and quantifies the accuracy limits imposed by non-Gaussianity, surpassing previous methods.

Findings

Non-Gaussianity limits lensing reconstruction accuracy.

Optimal sensitivity allows dark matter mapping with S/N > 1 up to l < 6000.

Improved estimators outperform previous deflection angle methods.

Abstract

We study the limits of accuracy for weak lensing maps of dark matter using diffuse 21-cm radiation from the pre-reionization epoch using simulations. We improve on previous "optimal" quadratic lensing estimators by using shear and convergence instead of deflection angles. We find that non-Gaussianity provides a limit to the accuracy of weak lensing reconstruction, even if instrumental noise is reduced to zero. The best reconstruction result is equivalent to Gaussian sources with effectively independent cell of side length 2.0/h Mpc. Using a source full map from z=10-20, this limiting sensitivity allows mapping of dark matter at a Signal-to-Noise ratio (S/N) greater than 1 out to l < 6000, which is better than any other proposed technique for large area weak lensing mapping.