Probing the matter-dominated expansion with multi-redshift Lyman-α BAO from DESI DR2
Abstract
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 zeff = 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.
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BibTeX
@misc{herreraalcantar2026probing,
title = {{Probing the matter-dominated expansion with multi-redshift Lyman-$α$ BAO from DESI DR2}},
author = {Hiram K. Herrera-Alcantar and Julien Guy and Alma X. Gonzalez-Morales and Eric Armengaud and Edwin L. Pérez-Ochoa and Cristhian Garcia-Quintero and J. Aguilar and S. Ahlen and F. Beutler and D. Bianchi and A. Brodzeller and D. Brooks and E. Chaussidon and T. Claybaugh and A. Cuceu and K. S. Dawson and A. de la Macorra and Arjun Dey and S. Ferraro and A. Font-Ribera and J. E. Forero-Romero and E. Gaztañaga and G. Gutierrez and C. Hahn and K. Honscheid and D. Huterer and M. Ishak and T. Karim and R. Kehoe and D. Kirkby and A. Kremin and O. Lahav and A. Lambert and M. Landriau and L. Le Guillou and M. Manera and P. Martini and A. Meisner and R. Miquel and J. Moustakas and A. Muñoz-Gutiérrez and S. Nadathur and G. Niz and E. Paillas and N. Palanque-Delabrouille and W. J. Percival and C. Poppett and F. Prada and I. Pérez-Ràfols and C. Ravoux and G. Rossi and R. Ruggeri and L. Samushia and E. Sanchez and C. Saulder and D. Schlegel and M. Schubnell and H. Seo and J. Silber and G. Tarlé},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2607.19619},
eprint = {2607.19619},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2607.19619},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Probing the matter-dominated expansion with multi-redshift Lyman-α BAO from DESI DR2
AU - Hiram K. Herrera-Alcantar
AU - Julien Guy
AU - Alma X. Gonzalez-Morales
AU - Eric Armengaud
AU - Edwin L. Pérez-Ochoa
AU - Cristhian Garcia-Quintero
AU - J. Aguilar
AU - S. Ahlen
AU - F. Beutler
AU - D. Bianchi
AU - A. Brodzeller
AU - D. Brooks
AU - E. Chaussidon
AU - T. Claybaugh
AU - A. Cuceu
AU - K. S. Dawson
AU - A. de la Macorra
AU - Arjun Dey
AU - S. Ferraro
AU - A. Font-Ribera
AU - J. E. Forero-Romero
AU - E. Gaztañaga
AU - G. Gutierrez
AU - C. Hahn
AU - K. Honscheid
AU - D. Huterer
AU - M. Ishak
AU - T. Karim
AU - R. Kehoe
AU - D. Kirkby
AU - A. Kremin
AU - O. Lahav
AU - A. Lambert
AU - M. Landriau
AU - L. Le Guillou
AU - M. Manera
AU - P. Martini
AU - A. Meisner
AU - R. Miquel
AU - J. Moustakas
AU - A. Muñoz-Gutiérrez
AU - S. Nadathur
AU - G. Niz
AU - E. Paillas
AU - N. Palanque-Delabrouille
AU - W. J. Percival
AU - C. Poppett
AU - F. Prada
AU - I. Pérez-Ràfols
AU - C. Ravoux
AU - G. Rossi
AU - R. Ruggeri
AU - L. Samushia
AU - E. Sanchez
AU - C. Saulder
AU - D. Schlegel
AU - M. Schubnell
AU - H. Seo
AU - J. Silber
AU - G. Tarlé
PY - 2026
DA - 2026/11/04
PB - arXiv
DO - 10.48550/arxiv.2607.19619
UR - https://arxiv.org/abs/2607.19619
AB - 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_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 D_V/r_d from 30.26±0.39 to 32.22±0.47 and in the Alcock-Paczyński parameter D_M/D_H from 3.96±0.15 to 5.63^+0.22_−0.24. The Hubble distance D_H/r_d 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 γ_α=3.05±0.16, the RSD parameter has a redshift evolution described by γ_β=−0.97±0.26, and the quasar bias evolves with γ_Q=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 w_0w_aCDM and improves curvature constraints by ∼12% in ΛCDM+Ω_K.
ER -