Forecasting galaxy cluster H i mass recovery with CHIME at redshifts z = 1 and 2 via the IllustrisTNG simulations

Abstract

ABSTRACT The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is a drift-scan interferometer designed to map the entire northern sky every 24 h. The all-sky coverage and sensitivity to neutral hydrogen flux at intermediate redshifts makes the instrument a resource for other exciting science in addition to cosmology for which it was originally designed. Here, we demonstrate its utility for the study of the H i content of galaxy populations across environments and redshifts. We use simulated data from the IllustrisTNG project to generate mock CHIME-like intensity maps, which we cross-correlate with various tracers – including galaxies and galaxy clusters – to recover aggregate H i signals from stacking analyses. We find that there is more flux in stacks on galaxy clusters or cluster member galaxies compared to those on a general galaxy catalogue due to the enhanced number of H i-rich sources included in the CHIME primary beam. We report that it is possible to infer an average $M_\mathrm{HI}$ for clusters as a function of redshift and selection criteria from the signal in their averaged stacks despite the instrument’s low spatial resolution. This proof-of-concept result opens up a promising, and timely, new avenue to measure the evolution of the neutral hydrogen content in intermediate-to-high redshift galaxy clusters via cross-correlation of galaxy cluster catalogues with 21-cm intensity maps.