High-redshift 21cm Cosmology in Canada

TL;DR

This paper discusses the potential of 21cm cosmology to explore the early universe's Dark Ages, Cosmic Dawn, and Reionization, emphasizing Canadian contributions and future research directions.

Contribution

It outlines a comprehensive strategy for Canadian involvement in 21cm cosmology, including experimental, analytical, and theoretical advancements, to maximize scientific returns.

Findings

Potential to constrain first-generation galaxy properties

Ability to measure the Hubble parameter at high redshift

Opportunities to test exotic physics like baryon-dark matter interactions

Abstract

In the next few years, the 21cm line will enable direct observations of the Dark Ages, Cosmic Dawn, and Reionization, which represent previously unexplored periods in our cosmic history. With a combination of sky-averaged global signal measurements and spatial mapping surveys, the possible science return is enormous. This potentially includes (but is not limited to) constraints on first-generation galaxies (such as their typical masses and luminosities), constraints on cosmological parameters, a measurement of the Hubble parameter at z~15 to 20, the elimination of the optical depth nuisance parameter in the CMB, and searches for exotic phenomena such as baryon-dark matter couplings. To enable continued Canadian leadership in these science opportunities, we recommend 1) continued investments in 21cm experiments at all redshifts, 2) detailed analysis efforts of current data to overcome systematic effects, 3) new investments in preliminary experiments to explore the truly low-frequency sky as a stepping stone towards the Dark Ages, 4) new investments in line-intensity mapping experiments beyond the 21cm line, 5) continued theory support for 21cm cosmology, and 6) continued participation and knowledge transfer to next-generation international efforts such as the Square Kilometre Array.