The gravitational and lensing-ISW bispectrum of 21cm radiation
Claude J. Schmit, Alan F. Heavens, Jonathan R. Pritchard
TL;DR
This paper analyzes the 21cm bispectrum from neutral hydrogen, exploring its potential to improve cosmological parameter constraints and assessing the significance of lensing-ISW effects for upcoming intensity mapping experiments.
Contribution
It provides the first detailed computation of the 21cm bispectrum from gravitational collapse and lensing-ISW effects, and forecasts its impact on cosmological parameter estimation.
Findings
Bispectrum observations can reduce parameter errors by an order of magnitude.
Lensing-ISW bispectrum can be neglected in 21cm analyses, unlike in CMB studies.
Upcoming surveys like CHIME, MeerKAT, and SKA-mid can significantly enhance cosmological constraints.
Abstract
Cosmic Microwave Background experiments from COBE to Planck, have launched cosmology into an era of precision science, where many cosmological parameters are now determined to the percent level. Next generation telescopes, focussing on the cosmological 21cm signal from neutral hydrogen, will probe enormous volumes in the low-redshift Universe, and have the potential to determine dark energy properties and test modifications of Einstein's gravity. We study the 21cm bispectrum due to gravitational collapse as well as the contribution by line of sight perturbations in the form of the lensing-ISW bispectrum at low-redshifts (), targeted by upcoming neutral hydrogen intensity mapping experiments. We compute the expected bispectrum amplitudes and use a Fisher forecast model to compare power spectrum and bispectrum observations of intensity mapping surveys by CHIME, MeerKAT and…
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