Baryon acoustic oscillations from the cross-correlation of Ly$\hat{I}\pm$ absorption and quasars in eBOSS DR14

Abstract

We present a measurement of the baryon acoustic oscillation (BAO) scale at redshift $z=2.35$ from the three-dimensional correlation of Lyman-$\hat{I}\pm$ (Ly$\hat{I}\pm$) 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$\hat{I}\pm$ absorption occurring in the Ly${\hat{I}}^2$ 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 $r_d$: $D_H(z=2.35)/r_d=9.20\pm 0.36$ and $D_M(z=2.35)/r_d=36.3\pm 1.8$. These results are consistent at $1.5\ddot{I}ƒ$ 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$\hat{I}\pm$ auto-correlation measurement presented in a companion paper, the BAO measurements at $z=2.34$ are within $1.7\ddot{I}ƒ$ of the predictions of this model.

18 pages, 14 figures, matches the published version by A&A