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Baryon acoustic oscillations from the cross-correlation of Ly\alpha absorption and quasars in eBOSS DR14

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(2019)cite arxiv:1904.03430Comment: 16 pages, 13 figures, submitted to A&A.

Abstract

We present a measurement of the baryon acoustic oscillation (BAO) scale at redshift $z=2.35$ from the three-dimensional correlation of Lyman-$\alpha$ (Ly$\alpha$) 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$\alpha$ absorption occurring in the Ly$\beta$ wavelength band of the spectra. From the measured BAO peak position along and across the line of sight, we determine the Hubble distance $D_H$ and the comoving angular diameter distance $D_M$ relative to the sound horizon at the drag epoch $r_d$: $D_H(z=2.35)/r_d=9.200.36$ and $D_M(z=2.35)/r_d=36.31.8$. These results are consistent at $1.5\sigma$ with the prediction of the best-fit flat $Łambda$CDM cosmological model reported for the Planck (2016) analysis of CMB anisotropies. Combined with the Ly$\alpha$ auto-correlation measurement presented in a companion paper (de Sainte Agathe et al. 2019) the BAO measurements at $z=2.34$ are within $1.7\sigma$ of the predictions of this model.

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