DESI DR2 Results I: Baryon Acoustic Oscillations from the Lyman Alpha Forest

Abstract

We present the Baryon Acoustic Oscillation (BAO) measurements with the Lyman-alpha (LyA) forest from the second data release (DR2) of the Dark Energy Spectroscopic Instrument (DESI) survey. Our BAO measurements include both the auto-correlation of the LyA forest absorption observed in the spectra of high-redshift quasars and the cross-correlation of the absorption with the quasar positions. The total sample size is approximately a factor of two larger than the DR1 dataset, with forest measurements in over 820,000 quasar spectra and the positions of over 1.2 million quasars. We describe several significant improvements to our analysis in this paper, and two supporting papers describe improvements to the synthetic datasets that we use for validation and how we identify damped LyA absorbers. Our main result is that we have measured the BAO scale with a statistical precision of 1.1% along and 1.3% transverse to the line of sight, for a combined precision of 0.65% on the isotropic BAO scale at $z_{eff}=2.33$. This excellent precision, combined with recent theoretical studies of the BAO shift due to nonlinear growth, motivated us to include a systematic error term in LyA BAO analysis for the first time. We measure the ratios $D_H(z_{eff})/r_d=8.632\pm 0.098\pm 0.026$ and $D_M(z_{eff})/r_d=38.99\pm 0.52\pm 0.12$, where $D_H=c/H(z)$ is the Hubble distance, $D_M$ is the transverse comoving distance, $r_d$ is the sound horizon at the drag epoch, and we quote both the statistical and the theoretical systematic uncertainty. The companion paper presents the BAO measurements at lower redshifts from the same dataset and the cosmological interpretation.

Accepted for publication in PRD. Updated authors and references. 29 pages and 13 figures. This DESI Collaboration Publication is part of the Data Release 2 publication series (see https://data.desi.lbl.gov/doc/papers )

Cited by in corpus (48)

• DESI DR2 Results II: Measurements of Baryon Acoustic Oscillations and Cosmological Constraints
• The CosmoVerse White Paper: Addressing observational tensions in cosmology with systematics and fundamental physics
• SPT-3G D1: CMB temperature and polarization power spectra and cosmology from 2019 and 2020 observations of the SPT-3G Main field
• Testing signatures of phantom crossing through full-shape galaxy clustering analysis
• Optimal parameterizations for observational constraints on thawing dark energy
• Dark Energy within the Generalized Uncertainty Principle in Light of DESI DR2
• Cosmographic Footprints of Dynamical Dark Energy
• Unified and consistent structure growth measurements from joint ACT, SPT and \textit{Planck} CMB lensing
• Robust Evidence for Dynamical Dark Energy from DESI Galaxy-CMB Lensing Cross-Correlation and Geometric Probes
• Neutrino mass tension or suppressed growth rate of matter perturbations?
• Testing Quintessence Axion Dark Energy with Recent Cosmological Results
• Non-minimally coupled gravity constraints from DESI DR2 data
• Bayesian and frequentist perspectives agree on dynamical dark energy
• Null energy condition violation and beyond Horndeski physics in light of DESI DR2 data
• One-loop power spectrum corrections in interacting dark energy cosmologies
• Joint Constraints on Neutrinos and Dynamical Dark Energy in Minimally Modified Gravity
• Dynamical Dark Energy and the Unresolved Hubble Tension: Multi-model Constraints from DESI 2025 and Other Probes
• Updated Cosmological Constraints from 2D BAO Measurements: A New Compilation and Comparison with DESI DR2
• Unified dark fluid with null sound speed as an alternative to phantom dark energy
• Constraints on the varying electron mass and early dark energy in light of ACT DR6 and DESI DR2 and the implications for inflation
• Thawing Quintessence: Priors, evidence, and likely trajectories
• $H_0$ Without the Sound Horizon (or Supernovae): A 2% Measurement in DESI DR1
• Lowering the Horizon on Dark Energy: A Late-Time Response to Early Solutions for the Hubble Tension
• The Compressed 3D Lyman-Alpha Forest Bispectrum
• The choice of Planck CMB likelihood in cosmological analyses
• Why $w\ne -1$? Anthropic Selection in a $\Lambda$ + Axion Dark Energy Model
• Cosmological Constraints on 4D Einstein-Gauss-Bonnet Gravity and Kaniadakis Holographic Dark Energy: Implications for Black Hole Shadows
• Testing the Cosmic Distance Duality Relation with Neural Kernel Gaussian Process Regression
• Cosmological Model Independent Constraints on Lorentz Invariance Violation with Updated Gamma-Ray Burst Observations: An Artificial Neural Network Approach
• Probing dynamical embeddings in a five-dimensional spacetime in light of DESI BAO
• Dark Energy After DESI DR2: Observational Status, Reconstructions, and Physical Models
• The Lyman-$\alpha$ Forest from LBGs: First 3D Correlation Measurement with DESI and Prospects for Cosmology
• Lya2pcf: an efficient pipeline to estimate two- and three-point correlation functions of the Lyman-$\alpha$ forest
• Web-Halo Model (WHM): Accurate non-linear matter power spectrum predictions without free parameters
• Generation of Lognormal Synthetic Lyman-$\alpha$ Forest Spectra for $P_{1D}$ Analysis
• Unified reconstruction of the Lyman-alpha power spectrum with Hamiltonian Monte Carlo
• Geometric formulation of $k$-essence and late-time acceleration
• DESI DR1 Lyα 1D power spectrum: The Fast Fourier Transform estimator measurement
• The Atacama Cosmology Telescope: A demonstration of CMB lensing measurement from daytime data
• Measurements of quasar proximity zones with the Ly$\alpha$ forest of DESI Y1 quasars
• Integrated Sachs-Wolfe maps from the Gower Street $w$CDM simulations
• Beyond thermal approximations: Precise cosmological bounds on Axion-Like Particles
• Constraining Quintessence Models with ISW-tSZ Cross-Correlations: A Comparative Analysis of Thawing, Tracker, and Scaling-Freezing Dynamics
• A Non-parametric Method for the Inference of Halo Occupation Distributions
• Statistical consistency of sign-switching vacuum energy with cosmological observations
• Charge diffusion and modulation transfer function in a Nancy Grace Roman Space Telescope detector
• Unifying the Dark Sector with the New Generalized Chaplygin Gas: Observational Constraints
• Sector-Resolved Bayesian Model Averaging for DESI-Era Cosmology