HI as a Probe of the Large Scale Structure in the Post-Reionization Universe: Visibility Correlations and Prospects for Detection

TL;DR

This paper evaluates the potential for detecting large-scale HI distribution in the post-reionization universe using radio telescopes, focusing on visibility correlations and direct detection prospects with MWA and GMRT.

Contribution

It demonstrates the feasibility of detecting HI signals and rare peaks through visibility correlations and direct detection methods with existing radio telescopes.

Findings

MWA can detect visibility correlations at high redshifts.

GMRT can detect at lower redshifts, especially around z=1.3.

Direct detection of rare HI peaks is possible within 1000 hours.

Abstract

Simulated maps of the HI distribution in the post-reionization era are used to study the prospects for detection with existing and upcoming radio telescopes. We consider detection in the redshifted radiation from the hyperfine transition with a rest frame frequency of 1420 MHz. Possibility of a statistical detection using visibility correlations is discussed. We show that the MWA (Murchison Widefield Array) and the GMRT (Giant Meterwave Radio Telescope) can potentially detect signal from the HI distribution at high redshifts. MWA can detect visibility correlations at large angular scales at all redshifts accessible to it in the post-reionization era. The GMRT can detect visibility correlations at lower redshifts, specifically there is a strong case for a survey at z = 1.3. We also discuss prospects for direct detection of rare peaks in the HI distribution using the GMRT. We show that direct detection should be possible with integration time that is comparable to, or even less than, the time required for a statistical detection. Specifically, it is possible to make a statistical detection of the HI distribution by measuring the visibility correlation, and, direct detection of rare peaks in the HI distribution using the GMRT in less than 1000 hours of observations.