Recombination-independent determination of the sound horizon and the Hubble constant from BAO

Levon Pogosian; Gong-Bo Zhao; Karsten Jedamzik

doi:10.3847/2041-8213/abc6a8

paper

Recombination-independent determination of the sound horizon and the Hubble constant from BAO

arXiv:2009.08455 · doi:10.3847/2041-8213/abc6a8

Abstract

The Hubble tension and attempts to resolve it by modifying the physics of (or at) recombination motivate finding ways to determine $H_{0}$ and the sound horizon at the epoch of baryon decoupling $r_{d}$ in ways that neither rely on a recombination model nor on late-time Hubble data. In this work, we investigate what one can learn from the current and future BAO data when treating $r_{d}$ and $H_{0}$ as independent free parameters. It is well known that BAO gives exquisite constraints on the product $r_{d} H_{0}$ . We show here that imposing a moderate prior on $Ω_{m} h^{2}$ breaks the degeneracy between $r_{d}$ and $H_{0}$ . Using the latest BAO data, including the recently released eBOSS DR16, along with a $Ω_{m} h^{2}$ prior based on the Planck best fit $Λ$ CDM model, we find $r_{d} = 143.7 \pm 2.7$ Mpc and $H_{0} = 69.6 \pm 1.8$ km/s/Mpc. BAO data therefore prefers somewhat lower $r_{d}$ and higher $H_{0}$ than those inferred from Planck data in a $Λ$ CDM model. We find similar values when combing BAO with the Pantheon supernovae, DES galaxy weak lensing, Planck or SPTPol CMB lensing and the cosmic chronometers data. We perform a forecast for DESI and find that, when aided with a moderate prior on $Ω_{m} h^{2}$ , DESI will measure $r_{d}$ and $H_{0}$ without assuming a recombination model with an accuracy surpassing the current best estimates from Planck.

8 pages, 4 figures, 2 tables; v2: minor revisions, references added, matches the version accepted to Ap J Lett

Recombination-independent determination of the sound horizon and the Hubble constant from BAO

Abstract

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