Combined lensed estimator to probe the post reionization H I power spectrum

TL;DR

This paper proposes a new method using gravitational lensing by galaxy clusters to measure the post-reionization H I power spectrum, demonstrating its potential effectiveness with specific observational setups and addressing foreground challenges.

Contribution

It introduces a combined lensed estimator for the H I power spectrum and evaluates its efficacy using galaxy cluster lensing data, advancing observational techniques in the post-reionization era.

Findings

Possible to estimate the H I power spectrum at 5-sigma significance for certain angular scales.

Combining data from multiple galaxy clusters improves measurement accuracy.

Foreground suppression is possible but still requires careful mitigation.

Abstract

In the post-reionization era, the baryons assembled into the protogalaxies and eventually the present population of the galaxies evolved through merger and evolution. In this work, we discuss a possible probe of the statistical distribution and evolution of the H I density in the post reionization era. We introduce an estimator of the H I power spectrum from the post reionization universe by observing it through the strong gravitational lenses by the nearby galaxy cluster. We also analytically calculate the uncertainties associated with the estimates of the post-EoR power spectrum for the discussed estimator. We access the efficacy of this estimator in the context of 19 galaxy clusters for which the lensing potential has been estimated earlier by various authors. We find that by combining the lensed power spectrum through eight of these cluster lenses, it is possible to estimate the post-reionization H I power spectrum at five-sigma significance for angular multipoles < 4000 for a uGMRT observation of 16 MHz bandwidth from redshifts of 1.25, 1.5 with a total of 400 hours of observation. With the same setup, for a redshift of 3.0, we need 200 hours of total observation time. The estimator also suppresses the diffused galactic foreground, though, the latter is still a dominant contributor to the overall signal and hence need to be estimated and mitigated. We discuss the merits and demerits of the estimator.