2026/07/21 by Hiram K. Herrera-Alcantar, Julien Guy, Alma X. Gonzalez-Morales +60
#astro-ph.CO
We present a multi-redshift Baryon Acoustic Oscillations (BAO) analysis of the DESI Data Release 2 (DR2) Lyman-α (Lyα) forest, splitting the forest auto-correlation and its cross-correlation with quasars into three redshift bins. We obtain BAO measurements at effective redshifts z\rm eff = 2.13, 2.40, and 2.81 with ∼2.0--2.5% precision per bin in the radial and transverse directions, corresponding to ∼1.1--1.2% precision for the isotropic BAO measurement. Using the same data products and modeling framework as the DESI DR2 Lyα BAO analysis, we validate the pipeline on 400 synthetic datasets and find unbiased BAO recovery with well-calibrated uncertainties. The measurements show an increase in the isotropic dilation parameter DV/rd from 30.26±0.39 to 32.22±0.47 and in the Alcock-Paczyński parameter DM/DH from 3.96±0.15 to 5.63+0.22-0.24. The Hubble distance DH/rd decreases from 9.40±0.20 to 7.22±0.17, providing a direct measurement of the expansion history consistent with ΛCDM and the expected matter-dominated scaling, with H(z)∝(1+z)n giving n=1.34±0.16. The redshift split also provides a self-consistent measurement of clustering evolution: the Lyα forest bias evolves as (1+z)γ with γα=3.05±0.16, the RSD parameter has a redshift evolution described by γβ=-0.97±0.26, and the quasar bias evolves with γQ=1.56±0.23, consistent with independent quasar clustering measurements. Combining these three-bin BAO measurements with DESI DR2 galaxy and quasar BAO measurements yields cosmological constraints consistent with the single-bin Lyα BAO analysis in flat ΛCDM and w0waCDM and improves curvature constraints by ∼12% in ΛCDM+ΩK.