Lensing contribution to the 21cm intensity bispectrum

TL;DR

This paper calculates how gravitational lensing by large-scale structures affects the 21cm intensity bispectrum across the sky, revealing that lensing can significantly influence measurements at high redshifts.

Contribution

It extends previous models by computing the lensing contribution to the full-sky 21cm bispectrum in redshift space, highlighting its importance at high redshifts.

Findings

Lensing peaks when equal-redshift fluctuations are lensed by lower redshift ones.

Lensing effects can match density and redshift-space distortion contributions at high redshift.

Lensing impacts the interpretation of 21cm bispectrum measurements.

Abstract

Intensity maps of the 21cm emission line of neutral hydrogen are lensed by intervening large-scale structure, similar to the lensing of the cosmic microwave background temperature map. We extend previous work by calculating the lensing contribution to the full-sky 21cm bispectrum in redshift space. The lensing contribution tends to peak when equal-redshift fluctuations are lensed by a lower redshift fluctuation. At high redshift, lensing effects can become comparable to the contributions from density and redshift-space distortions.