Determining the Hubble Constant without the Sound Horizon: Measurements from Galaxy Surveys

TL;DR

This paper presents a novel method to measure the Hubble constant using galaxy survey data that bypasses reliance on the sound horizon scale, providing an independent consistency check for standard cosmology.

Contribution

The authors introduce a technique to constrain H0 from galaxy surveys without using the sound horizon, offering a new approach to address the H0 tension.

Findings

Constraints on H0 around 65 km/s/Mpc from galaxy data.

Results are consistent with other measurements excluding the sound horizon.

Forecasts suggest future surveys could measure H0 with 1.6 km/s/Mpc precision.

Abstract

Two sources of geometric information are encoded in the galaxy power spectrum: the sound horizon at recombination and the horizon at matter-radiation equality. Analyzing the BOSS DR12 galaxy power spectra using perturbation theory with $\Omega_m$ priors from Pantheon supernovae but no priors on $\Omega_b$, we obtain constraints on $H_0$ from the second scale, finding $H_0 = 65.1^{+3.0}_{-5.4}\,\mathrm{km}\,\mathrm{s}^{-1}\mathrm{Mpc}^{-1}$; this differs from the best-fit of SH0ES at 95\% confidence. Similar results are obtained if $\Omega_m$ is constrained from uncalibrated BAO: $H_0 = 65.6^{+3.4}_{-5.5}\,\mathrm{km}\,\mathrm{s}^{-1}\mathrm{Mpc}^{-1}$. Adding the analogous lensing results from Baxter \& Sherwin 2020, the posterior shifts to $70.6^{+3.7}_{-5.0}\,\mathrm{km}\,\mathrm{s}^{-1}\mathrm{Mpc}^{-1}$. Using mock data, Fisher analyses, and scale-cuts, we demonstrate that our constraints do not receive significant information from the sound horizon scale. Since many models resolve the $H_0$ controversy by adding new physics to alter the sound horizon, our measurements are a consistency test for standard cosmology before recombination. A simple forecast indicates that such constraints could reach $\sigma_{H_0} \simeq 1.6\,\mathrm{km}\,\mathrm{s}^{-1}\mathrm{Mpc}^{-1}$ in the era of Euclid.