Constraints on the Cosmic Expansion Rate at Redshift 2.3 from the Lyman-α Forest

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. Using the flat A cold dark matter model we determine the matter density to be SZm = 0.36 thorn 0.03 -0.04 from Ly alpha alone. This is a factor of 2 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 Mpc). Using a nucleosynthesis prior, we measure the Hubble constant to be H0 = 63.2 +/- 2.5 km/s/Mpc. In combination with other SDSS tracers, we find H0 = 67.2 +/- 0.9 km/s/Mpc and measure the dark energy equation-of-state parameter to be w = -0.90 +/- 0.12. Our Letter opens a new avenue for constraining cosmology at high redshift.

Automated summary

We determine the product of the expansion rate and angular-diameter distance at redshift z = 2.3 from Lyman-alpha forest correlations measured by the Sloan Digital Sky Survey. Our result is the most precise from large-scale structure at z > 1. Using a cold dark matter model, we determine the matter density and the Hubble constant to be SZm = 0.36 ± 0.03 -0.04 and H0 = 63.2 ± 2.5 km/s/Mpc, respectively. Combining with other SDSS tracers, we find H0 = 67.2 ± 0.9 km/s/Mpc and measure the dark energy equation-of-state parameter to be w = -0.90 ± 0.12. Our Letter opens a new avenue for constraining cosmology at high redshift.