Quasar-Lyman α forest cross-correlation from BOSS DR11: Baryon Acoustic Oscillations

We measure the large-scale cross-correlation of quasars with the Lyα forest absorption, using over 164,000 quasars from Data Release 11 of the SDSS-III Baryon Oscillation Spectroscopic Survey. We extend the previous study of roughly 60,000 quasars from Data Release 9 to larger separations, allowing a measurement of the Baryonic Acoustic Oscillation (BAO) scale along the line of sightc/(H(z= 2.36)rs) = 9.0±0.3 and across the line of sightDA(z= 2.36)/rs= 10.8±0.4, consistent with CMB and other BAO data. Using the best fit value of the sound horizon from Planck data (rs= 147.49 Mpc), we can translate these results to a measurement of the Hubble parameter ofH(z= 2.36) = 226±8 km s−1 Mpc−1and of the angular diameter distance ofDA(z= 2.36) = 1590±60 Mpc. The measured cross-correlation function and an update of the code to fit the BAO scale (baofit) are made publicly available.