Synergizing 21 cm and sub-millimetre surveys during reionization: new empirical insights

TL;DR

This paper explores the potential of cross-correlating 21 cm and submillimetre surveys during reionization, using recent ALMA data to predict the evolution of key emission lines and assess detectability with upcoming instruments.

Contribution

It provides empirical insights into the evolution of [CII] and [OIII] emissions during reionization and evaluates the prospects for detecting their cross-correlations with 21 cm surveys.

Findings

Secure detection of [CII] auto-power spectrum at high redshifts.

Potential to measure 21 cm - [CII] cross-correlation with future telescopes.

Detectability of 21 cm - [OIII] cross-correlation up to z~7.

Abstract

We use the latest results from Atacama Large Millimetre/submillimetre Array (ALMA) surveys targeting the ionized carbon [CII] 158 $\mu$m and oxygen [OIII] 88 $\mu$m lines, in combination with data-driven predictions for the evolution of neutral hydrogen (HI), to illustrate the prospects for intensity mapping cross-correlations between 21 cm and submillimetre surveys over $z \sim 5-7$. We work with a dataset including the ALPINE and REBELS surveys for [CII] over $z \sim 4.5-7$, and ALMA [OIII] detections over $z \sim 6-9$. The resultant evolution of the [CII] luminosity - halo mass relation is well described by a double power law at high redshifts, with the best-fitting parameters in good agreement with the results of simulations. The data favour secure detections of the auto-power spectrum of [CII] at all redshifts with an enhanced Fred Young Submillimetre Telescope (FYST)-like configuration. Such an experiment, along with the Murchinson Widefield Array (MWA) will be able to measure the 21 cm - [CII] cross-correlation power with a signal-to-noise ratio of a few tens to a few hundreds. We find that a balloon-borne experiment improving upon the Experiment for Cryogenic Large-Aperture Intensity Mapping (EXCLAIM) should be able to detect the 21 cm - [OIII] cross-correlation with the MWA and the Square Kilometre Array (SKA)-LOW out to $z \sim 7$. Our results have implications for constraining the evolution of luminous sources during the mid-to-end stages of reionization.