# Baryon acoustic oscillations at z = 2.34 from the correlations of Ly$\alpha$ absorption in eBOSS DR14

## TL;DR

This paper measures baryon acoustic oscillations at redshift 2.34 using Lyα absorption in quasar spectra from SDSS DR14, providing constraints on cosmological distances consistent with the flat-ΛCDM model.

## Contribution

First measurement of BAO in Lyα absorption including the Lyman-β region at z=2.34, improving distance constraints and confirming consistency with CMB-based cosmological models.

## Key findings

- Measured D_H(2.34)/r_d=8.86±0.29
- Measured D_M(2.34)/r_d=37.41±1.86
- Results are within 1σ of flat-ΛCDM predictions

## Abstract

We measure the imprint of primordial baryon acoustic oscillations (BAO) in the correlation function of Ly$\alpha$ absorption in quasar spectra from the Baryon Oscillation Spectroscopic Survey (BOSS) and the extended BOSS (eBOSS) in Data Release 14 (DR14) of the Sloan Digital Sky Survey (SDSS)-IV. In addition to 179,965 spectra with absorption in the Lyman-$\alpha$ (Ly$\alpha$) region, we use, for the first time, Ly$\alpha$ absorption in the Lyman-$\beta$ region of 56,154 spectra. We measure the Hubble distance, $D_H$, and the comoving angular diameter distance, $D_M$, relative to the sound horizon at the drag epoch $r_d$ at an effective redshift $z=2.34$. Using a physical model of the correlation function outside the BAO peak, we find $D_H(2.34)/r_d=8.86\pm 0.29$ and $D_M(2.34)/r_d=37.41\pm 1.86$, within 1$\sigma$ from the flat-$\Lambda$CDM model consistent with CMB anisotropy measurements. With the addition of polynomial "broadband" terms, the results remain within one standard deviation of the CMB-inspired model. Combined with the quasar-Ly$\alpha$ cross-correlation measurement presented in a companion paper Blomqvist19, the BAO measurements at $z=2.35$ are within 1.7$\sigma$ of the predictions of this model.