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

Area of Science:

• Cosmology
• Astrophysics
• Large-scale structure

Background:

• Cosmological parameters are crucial for understanding the universe's evolution.
• Previous measurements at high redshift (z>1) have limitations in precision.
• Lyman-alpha (Lyα) forest correlations offer a probe of cosmic structure.

Purpose of the Study:

• To determine the product of expansion rate and angular-diameter distance at z=2.3.
• To constrain cosmological parameters, including matter density and the dark energy equation-of-state parameter.
• To establish Lyα forest correlations as a precise tool for high-redshift cosmology.

Main Methods:

• Analysis of Lyman-alpha (Lyα) forest correlations from the Sloan Digital Sky Survey (SDSS).
• Utilizing a wide range of scales (25
• Incorporating a nucleosynthesis prior for Hubble constant determination.

Main Results:

• The most precise measurement of expansion rate and angular-diameter distance product at z=2.3 from large-scale structure.
• Matter density (Ωm) determined as 0.36 ± 0.03, twice as tight as baryon acoustic oscillation results.
• Hubble constant (H₀) measured as 63.2 ± 2.5 km/s/Mpc (Lyα alone) and 67.2 ± 0.9 km/s/Mpc (with other SDSS tracers).
• Dark energy equation-of-state parameter (w) measured as -0.90 ± 0.12.

Conclusions:

• Lyman-alpha forest correlations provide a powerful new method for constraining cosmology at high redshift.
• The study yields highly precise cosmological parameters, improving upon existing measurements.
• This research opens a new frontier for exploring the universe's expansion history.