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A Standard Ruler at Cosmic Dawn

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arxiv 1904.07868 v2 pith:FUCDUT5X submitted 2019-04-16 astro-ph.CO hep-ph

classification astro-ph.COhep-ph
keywords acousticcosmicdawndarkduringexpansionformationmatter
verification ladder T0 review T1 audit T2 compute T3 formal

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abstract

The matter in our Universe comes in two flavors: dark and baryonic. Of these, only the latter couples to photons, giving rise to the well-known baryon acoustic oscillations and, in the process, generating supersonic relative velocities between dark matter and baryons. These velocities---imprinted with the acoustic scale in their genesis---impede the formation of the first stars during cosmic dawn ($z\sim 20$), modulating the expected 21-cm signal from this era. In a companion paper we showed, combining numerical simulations and analytic models, that this modulation takes the form of robust velocity-induced acoustic oscillations (VAOs), with a well-understood shape that is frozen at recombination, and unaffected by the unknown astrophysics of star formation. Here we propose using these VAOs as a standard ruler at cosmic dawn. We find that three years of 21-cm power-spectrum data from the upcoming HERA interferometer should be able to measure the Hubble expansion rate $H(z)$ at $z=15-20$ to percent-level precision, ranging from $0.3\%$ to $11\%$ depending on the strength of astrophysical feedback processes and foregrounds. This would provide a new handle on the expansion rate of our Universe during an otherwise unprobed epoch, opening a window to the mysterious cosmic-dawn era.

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Forward citations

Cited by 3 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

  1. The Rise and Fall of Acoustic Oscillations at Cosmic Dawn

    astro-ph.CO 2026-07 conditional novelty 7.0 of 10

    Ignoring the percent-level phase offset between BAO and VAO features in the cosmic-dawn 21-cm power spectrum biases H(z) by ~2%; joint BAO–VAO templates are required for standard-ruler inference.

  2. Tracing the Neutrino-Induced Phase Shift in the 21-cm Spectrum

    astro-ph.CO 2025-09 conditional novelty 6.0 of 10

    The neutrino-induced phase shift in the 21-cm power spectrum is a redshift- and scale-dependent weighted average of two distinct templates: the known BAO phase shift and a newly computed, larger VAO phase shift.

  3. An Alcock-Paczynski Test on Reionization Bubbles for Cosmology

    astro-ph.CO 2025-02 conditional novelty 6.0 of 10

    Stacks of reionization HII bubbles act as standard spheres, allowing a forecast ~2% measurement of D_A H at z=7.5 with SKA-like 21-cm data.

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