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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

A Standard Ruler at Cosmic Dawn

classification astro-ph.CO hep-ph
keywords acousticcosmicdawndarkduringexpansionformationmatter
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved
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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.

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

    astro-ph.CO 2026-07 conditional novelty 7.0

    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. Cosmological searches for the neutrino mass scale and mass ordering

    astro-ph.CO 2019-07 unverdicted novelty 4.0

    Thesis summarizing an upper limit of 0.12 eV on the neutrino mass sum, bias calibration via CMB lensing cross-correlations, and tighter limits plus stronger normal-ordering preference in non-phantom dynamical dark ene...

  3. The Hubble Tension and Early Dark Energy

    astro-ph.CO 2022-11 unverdicted novelty 2.0

    The Hubble tension between local and early-universe expansion-rate measurements may be resolved by early dark energy that speeds up expansion before recombination while satisfying existing constraints.