Constraints on the cosmic expansion rate at redshift 2.3 from the Lyman-$\alpha$ forest

TL;DR

This paper measures the cosmic expansion rate at redshift 2.3 using Lyman-alpha forest data from SDSS, providing precise constraints on cosmological parameters and demonstrating a new method for high-redshift cosmology.

Contribution

It presents the most precise measurement of the expansion rate at z=2.3 from large-scale structure, using Lyman-alpha forest anisotropy, and tightens constraints on cosmological parameters.

Findings

Matter density Ω_m=0.36^{+0.03}_{-0.04} from Lyα alone.

Hubble constant H_0=63.2±2.5 km/s/Mpc with nucleosynthesis prior.

Combined SDSS data yields H_0=67.2±0.9 km/s/Mpc and w=-0.90±0.12.

Abstract

We determine the product of the expansion rate and angular-diameter distance at redshift $z=2.3$ from the anisotropy of Lyman-$\alpha$ (Ly$\alpha$) forest correlations measured by the Sloan Digital Sky Survey (SDSS). Our result is the most precise from large-scale structure at $z>1$. In flat $\Lambda$CDM we determine the matter density to be $\Omega_\mathrm{m}=0.36^{+0.03}_{-0.04}$ from Ly$\alpha$ alone. This is a factor of two tighter than baryon acoustic oscillation results from the same data due to our use of a wide range of scales ($25<r<180$ $h^{-1}\text{Mpc}$). Using a nucleosynthesis prior, we measure the Hubble constant to be $H_0=63.2\pm2.5$ km/s/Mpc. In combination with other SDSS tracers, we find $H_0=67.2\pm0.9$ km/s/Mpc and measure the dark energy equation-of-state parameter to be $w=-0.90\pm0.12$. Our work opens a new avenue for constraining cosmology at high redshift.