Lensing contribution to the 21 cm intensity bispectrum
Abstract
Intensity maps of the 21 cm 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 21 cm 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.