Neutral hydrogen lensing simulations in the Hubble Frontier Fields

TL;DR

This study uses gravitational lensing simulations to identify promising high HI mass systems in the Hubble Frontier Fields, enabling potential detection of neutral hydrogen at higher redshifts than previously possible.

Contribution

We developed a ray-tracing simulation method for lensed HI images, identifying promising targets like the Great Arc in Abell 370 for future observations.

Findings

High HI mass, high magnification systems exist in cluster lensing scenarios.

The most promising candidate, the Great Arc in Abell 370, can be detected with MeerKAT in ~50 hours.

HI mass estimates are robust against lensing model uncertainties, within a factor of ~2.5.

Abstract

Cold gas evolution ties the formation of dark matter halos to the star formation history of the universe. A primary component of cold gas, neutral atomic hydrogen (HI), can be traced by its 21-cm emission line. However, the faintness of this emission typically limits individual detections to low redshifts ($z\lesssim 0.2$). To address this limitation, we investigate the potential of targeting gravitationally lensed systems. Building on our prior galaxy-galaxy simulations, we have developed a ray-tracing code to simulate lensed HI images for known galaxies situated behind the massive Hubble Frontier Field galaxy clusters. Our findings reveal the existence of high HI mass, high HI magnification systems in these cluster lensing scenarios. Through simulations of hundreds of sources, we have identified compelling targets within the redshift range $z\approx 0.7 - 1.5$. The most promising candidate from our simulations is the Great Arc at z=0.725 in Abell~370, which should be detectable by MeerKAT in approximately 50 hours. Importantly, the derived HI mass is predicted to be relatively insensitive to systematic uncertainties in the lensing model, and should be constrained within a factor of $\sim 2.5$ for a 95 per cent confidence interval.