The 6dF Galaxy Survey: baryon acoustic oscillations and the local Hubble constant

We analyse the large-scale correlation function of the 6dF Galaxy Survey (6dFGS) and detect a baryon acoustic oscillation (BAO) signal at 105 h -1 Mpc. The 6dFGS BAO detection allows us to constrain the distance-redshift relation at z eff = 0.106. We achieve a distance measure of D V (z eff ) = 457 27 Mpc and a measurement of the distance ratio, r s (z d )/D V (z eff ) = 0.336 0.015 (4.5 per cent precision), where r s (z d ) is the sound horizon at the drag epoch z d . The loweffective redshift of 6dFGS makes it a competitive and independent alternative to Cepheids and low-z supernovae in constraining the Hubble constant. We find a Hubble constant of H 0 = 67 3.2 km s -1 Mpc -1 (4.8 per cent precision) that depends only on the Wilkinson Microwave Anisotropy Probe-7 (WMAP-7) calibration of the sound horizon and on the galaxy clustering in 6dFGS. Compared to earlier BAO studies at higher redshift, our analysis is less dependent on other cosmological parameters. The sensitivity to H 0 can be used to break the degeneracy between the dark energy equation of state parameter w and H 0 in the cosmic microwave background data. We determine that w = -0.97 0.13, using only WMAP-7 and BAO data from both 6dFGS and