Testing Low-Redshift Cosmic Acceleration with Large-Scale Structure

Abstract

We examine the cosmological implications of measurements of the void-galaxy cross-correlation at redshift $z=0.57$ combined with baryon acoustic oscillation (BAO) data at $0.1<z<2.4$. We find direct evidence of the late-time acceleration due to dark energy at $>10\sigma$ significance from these data alone, independent of the cosmic microwave background and supernovae. Using a nucleosynthesis prior on $\Omega_bh^2$, we measure the Hubble constant to be $H_0=72.3\pm1.9\;{\rm km\,s}^{-1}{\rm Mpc}^{-1}$ from BAO+voids at $z<2$, and $H_0=69.0\pm1.2\;{\rm km\,s}^{-1}{\rm Mpc}^{-1}$ when adding Lyman-$\alpha$ BAO at $z=2.34$, both independent of the CMB. Adding voids to CMB, BAO and supernova data greatly improves measurement of the dark energy equation of state, increasing the figure of merit by >40%, but remaining consistent with flat flat $\Lambda$ cold dark matter.