Constraints on the Cosmic Expansion Rate at Redshift 2.3 from the Lyman-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>α</mml:mi></mml:mrow></mml:math> Forest
Andrei Cuceu, Andreu Font-Ribera, S. Nadathur, Benjamin Joachimi, Paul Martini
Abstract
We determine the product of the expansion rate and angular-diameter distance at redshift $z=2.3$ from the anisotropy of Lyman-$\ensuremath{\alpha}$ ($\mathrm{Ly}\ensuremath{\alpha}$) 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 $\mathrm{\ensuremath{\Lambda}}$ cold dark matter model we determine the matter density to be ${\mathrm{\ensuremath{\Omega}}}_{m}=0.3{6}_{\ensuremath{-}0.04}^{+0.03}$ from $\mathrm{Ly}\ensuremath{\alpha}$ 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 ($25<r<180\text{ }\text{ }{h}^{\ensuremath{-}1}\text{ }\mathrm{Mpc}$). Using a nucleosynthesis prior, we measure the Hubble constant to be ${H}_{0}=63.2\ifmmode\pm\else\textpm\fi{}2.5\text{ }\text{ }\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$. In combination with other SDSS tracers, we find ${H}_{0}=67.2\ifmmode\pm\else\textpm\fi{}0.9\text{ }\text{ }\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$ and measure the dark energy equation-of-state parameter to be $w=\ensuremath{-}0.90\ifmmode\pm\else\textpm\fi{}0.12$. Our Letter opens a new avenue for constraining cosmology at high redshift.