Estimation of Cosmological Parameters from HI Observations of Post-reionization Epoch

TL;DR

This paper demonstrates that HI observations of the post-reionization epoch can effectively constrain cosmological parameters, offering a complementary method to existing probes for understanding the universe's expansion and dark energy.

Contribution

It introduces a novel approach using diffuse HI emission fluctuations to estimate key cosmological parameters with high precision.

Findings

Parameter estimation accuracy comparable to supernova and galaxy surveys

Potential to probe a wide redshift range beyond current methods

Future HI observations can complement existing cosmological probes

Abstract

The emission from neutral hydrogen (HI) clouds in the post-reionization era (z < 6), too faint to be individually detected, is present as a diffuse background in all low frequency radio observations below 1420 MHz. The angular and frequency fluctuations of this radiation (~ 1 mK) is an important future probe of the large scale structures in the Universe. We show that such observations are a very effective probe of the background cosmological model and the perturbed Universe. In our study we focus on the possibility of determining the redshift space distortion parameter, coordinate distance and its derivative with redshift. Using reasonable estimates for the observational uncertainties and configurations representative of the ongoing and upcoming radio interferometers, we predict parameter estimation at a precision comparable with supernova Ia observations and galaxy redshift surveys, across a wide range in redshift that is only partially accessed by other probes. Future HI observations of the post-reionization era present a new technique, complementing several existing one, to probe the expansion history and to elucidate the nature of the dark energy.