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 km2 (corresponding to 400,000 stations), which, with a 1,000 h integration, would exceed the same global case by a factor of ~2. 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.
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Data availability
The data are available upon request from the corresponding author. Source data are provided with this paper.
Code availability
CAMB is available at http://camb.info, emcee is available at https://github.com/dfm/emcee and corner is available at https://github.com/dfm/corner.py. The analyses were performed in Python using publicly available routines in NumPy (https://numpy.org) and Matplotlib (https://matplotlib.org). All other codes used are available upon request from the corresponding author.
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Acknowledgements
We thank A. Lewis and L. V. E. Koopmans for their useful discussions. R.M. is supported by the Israel Academy of Sciences and Humanities & Council for Higher Education Excellence Fellowship Program for International Postdoctoral Researchers. We acknowledge the support of the Israel Science Foundation (grant no. 2359/20).
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R.B. initiated the project. R.M. performed the calculations, made the figures and wrote the paper in consultation with R.B.
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Mondal, R., Barkana, R. Prospects for precision cosmology with the 21 cm signal from the dark ages. Nat Astron 7, 1025–1030 (2023). https://doi.org/10.1038/s41550-023-02057-y
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DOI: https://doi.org/10.1038/s41550-023-02057-y
