Measuring the cosmic expansion rate using 21-cm velocity acoustic oscillations

Debanjan Sarkar and Ely D. Kovetz
Phys. Rev. D 107, 023524 – Published 24 January 2023

Abstract

The fluctuations in the dark matter-baryon relative velocity field are imprinted as acoustic oscillations in the 21-cm power spectrum during cosmic dawn (CD). These velocity acoustic oscillations (VAOs) keep the imprints of the comoving sound horizon scale. In a previous work by Muñoz, it has been demonstrated that these VAOs can be treated as standard rulers to measure the cosmic expansion rate at high redshifts by considering a variety of Lyman-Werner feedback strengths and foreground contamination scenarios. Here we extend that analysis by using a modified version of the public code 21cmfast. We use this code to simulate the VAOs in 21-cm power spectrum and forecast the potential to constrain H(z) with the HERA radio telescope, taking into account the effects of Lyman-α heating, Lyman-Werner feedback and foregrounds, the dependence on various astrophysical parameters, and the degeneracy with cosmological parameters. We find that H(z) can be measured with HERA at 0.36% relative accuracy in the range 11<z<20, under different astrophysical and foreground scenarios, with uncertainties in the Planck cosmological parameters setting a 0.080.2% relative-error floor in the measurement. This accuracy is on par with most low-redshift measurements and can be helpful in testing various cosmological scenarios motivated by the ongoing “Hubble tension.”

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  • Received 8 November 2022
  • Accepted 9 January 2023

DOI:https://doi.org/10.1103/PhysRevD.107.023524

© 2023 American Physical Society

Physics Subject Headings (PhySH)

Gravitation, Cosmology & Astrophysics

Authors & Affiliations

Debanjan Sarkar* and Ely D. Kovetz

  • Physics Department, Ben-Gurion University of the Negev, Beersheba 84105, Israel

  • *debanjan@post.bgu.ac.il
  • kovetz@bgu.ac.il

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Issue

Vol. 107, Iss. 2 — 15 January 2023

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