Prospects for precision cosmology with the 21 cm signal from the dark ages

TL;DR

This paper evaluates the potential of 21 cm observations from the dark ages to significantly improve cosmological parameter measurements, outlining the requirements and benefits of various experimental configurations.

Contribution

It quantifies the expected precision of cosmological parameters from 21 cm signals and establishes baseline requirements for future lunar and space-based experiments.

Findings

A 1,000 h global 21 cm measurement achieves 10% parameter precision.

A 10,000 h global measurement improves to 3.2% and constrains helium fraction to 9.9%.

A 10 km² array with 1,000 h integration surpasses global measurement precision.

Abstract

The 21 cm signal from the dark ages provides a potential new probe of fundamental cosmology. While exotic physics could be discovered, here we quantify the expected benefits within the standard cosmology. A measurement of the global (sky-averaged) 21 cm signal to the precision of thermal noise from a 1,000 h integration would yield a measurement within 10% of a combination of cosmological parameters. A 10,000 h integration would improve this measurement to 3.2% and constrain the cosmic helium fraction to 9.9%. Precision cosmology with 21 cm fluctuations requires a collecting area of 10 km$^2$ (corresponding to 400,000 stations), which, with a 1,000 h integration, would exceed the same global case by a factor of $\sim2$. Enhancing the collecting area or integration time by an order of magnitude would yield a 0.5% parameter combination, a helium measurement five times better than Planck and a constraint on the neutrino mass as good as Planck. Our analysis sets a baseline for upcoming lunar and space-based dark-ages experiments.