Measuring the Hubble constant through the galaxy pairwise peculiar velocity

TL;DR

This paper presents a novel method to measure the Hubble constant using galaxy pairwise velocities from Cosmicflows-4 data, achieving competitive precision and offering insights into cosmic expansion.

Contribution

First measurement of Hubble constant via galaxy pairwise velocities in the nonlinear regime, providing a new independent approach in cosmology.

Findings

H_0 = 75.5 ± 1.4 km/s/Mpc from pairwise velocities

Estimated matter density Ω_m = 0.311^{+0.029}_{-0.028}

Potential to improve uncertainties to 0.6% for H_0 and 2% for Ω_m

Abstract

The Hubble constant $H_0$, the current expansion rate of the universe, is one of the most important parameters in cosmology. The cosmic expansion regulates the mutually approaching motion of a pair of celestial objects due to their gravity. Therefore, the mean pairwise peculiar velocity of celestial objects, which quantifies their relative motion, is sensitive to both $H_0$ and the dimensionless total matter density $\Omega_m$. Based on this, using the Cosmicflows-4 data, we measured $H_0$ for the first time via the galaxy pairwise velocity in the nonlinear and quasi-linear range. Our results yield $H_0=75.5\pm1.4$ km s$^{-1}$ Mpc$^{-1}$ and $\Omega_m=0.311^{+0.029}_{-0.028}$ . The uncertainties of $H_0$ and $\Omega_m$ can be improved to around 0.6% and 2%, respectively, if the statistical errors become negligible in the future.