HI in and behind the Hubble Frontier Field Clusters: A Deep MeerKAT Pilot Search out to $z\sim 0.5$

TL;DR

This study uses MeerKAT radio observations to investigate neutral hydrogen in galaxy clusters at intermediate redshifts, achieving a stacked detection in one cluster and setting limits in others, demonstrating future potential for such research.

Contribution

First deep MeerKAT HI observations of Hubble Frontier Field clusters, including spectral-line stacking and gravitational lensing searches at intermediate redshifts.

Findings

Detected HI in blue galaxies of Abell S1063 via stacking.

Set HI mass detection limits at the knee of the HI Mass Function.

No evidence of highly magnified HI emission was found.

Abstract

The Hubble Frontier Fields (HFF) are a selection of well-studied galaxy clusters used to probe dense environments and distant gravitationally lensed galaxies. We explore the 21cm neutral hydrogen (HI) content of galaxies in three of the HFF clusters, Abell 2744 ($z = 0.308$), Abell S1063 ($z = 0.346$) and Abell 370 ($z = 0.375$), to investigate the evolution of gas in galaxies within intermediate redshift clusters. Using Early Science MeerKAT observations, we perform spectral-line stacking with HI cubes and make a 3$\sigma$ stacked detection for blue galaxies in Abell S1063 ($M_\mathrm{HI} = 1.22^{+0.38}_{-0.36}\times 10^{10} \mathrm{M}_\odot$). We determine the 3$\sigma$ HI mass detection limits of Abell 2744 and Abell 370 to be at the knee of the HI Mass Function. A final, more ambitious objective of this work is to search for gravitationally lensed HI emission behind these clusters, enabled by MeerKAT's wide instantaneous bandwidth. We find no evidence of highly magnified HI emission at $0.33<z<0.58$. The low thermal noise levels achieved in these pilot observations, despite short integration times, highlights the enormous potential of future MeerKAT HI observations of dense environments and the intermediate-redshift Universe.