Baryon acoustic oscillations from the cross-correlation of Lyαabsorption and quasars in eBOSS DR14
We present a measurement of the baryon acoustic oscillation (BAO) scale at redshift z = 2.35 from the three-dimensional correlation of Lyman- α (Ly α ) forest absorption and quasars. The study uses 266 590 quasars in the redshift range 1.77 < z < 3.5 from the Sloan Digital Sky Survey (SDSS) Data Release 14 (DR14). The sample includes the first two years of observations by the SDSS-IV extended Baryon Oscillation Spectroscopic Survey (eBOSS), providing new quasars and re-observations of BOSS quasars for improved statistical precision. Statistics are further improved by including Ly α absorption occurring in the Ly β wavelength band of the spectra. From the measured BAO peak position along and across the line of sight, we determined the Hubble distance D H and the comoving angular diameter distance D M relative to the sound horizon at the drag epoch r d : D H ( z = 2.35)/ r d = 9.20 ± 0.36 and D M ( z = 2.35)/ r d = 36.3 ± 1.8. These results are consistent at 1.5 σ with the prediction of the best-fit spatially-flat cosmological model with the cosmological constant reported for the Planck (2016) analysis of cosmic microwave background anisotropies. Combined with the Ly α auto-correlation measurement presented in a companion paper, the BAO measurements at z = 2.34 are within 1.7 σ of the predictions of this model.