Probing the matter-dominated expansion with multi-redshift Lyman- alpha BAO from DESI DR2

arXiv:2607.19619 · astro-ph.CO · Submitted 2026-07-21 · Read on arXiv

Hiram K. Herrera-Alcantar, Julien Guy, Alma X. Gonzalez-Morales, Eric Armengaud, Edwin L. Pérez-Ochoa, Cristhian Garcia-Quintero, J. Aguilar, S. Ahlen, F. Beutler, D. Bianchi, A. Brodzeller, D. Brooks, E. Chaussidon, T. Claybaugh, A. Cuceu, K. S. Dawson, A. de la Macorra, Arjun Dey, S. Ferraro, A. Font-Ribera, J. E. Forero-Romero, E. Gaztañaga, G. Gutierrez, C. Hahn, K. Honscheid, D. Huterer, M. Ishak, T. Karim, R. Kehoe, D. Kirkby, A. Kremin, O. Lahav, A. Lambert, M. Landriau, L. Le Guillou, M. Manera, P. Martini, A. Meisner, R. Miquel, J. Moustakas, A. Muñoz-Gutiérrez, S. Nadathur, G. Niz, E. Paillas, N. Palanque-Delabrouille, W. J. Percival, C. Poppett, F. Prada, I. Pérez-Ràfols, C. Ravoux, G. Rossi, R. Ruggeri, L. Samushia, E. Sanchez, C. Saulder, D. Schlegel, M. Schubnell, H. Seo, J. Silber, G. Tarlé, B. A. Weaver, C. Yèche, R. Zhou

astro-ph.CO

Submitted: 2026-07-21

Comments: 35 pages, 15 figures

Code: https://github.com/igmhub/picca

License: http://creativecommons.org/licenses/by/4.0/

The gist: We present a multi-redshift Baryon Acoustic Oscillations (BAO) analysis of the DESI Data Release 2 (DR2) Lyman- alpha (Ly alpha) forest, splitting the forest auto-correlation and its

Terminology

Abstract

We present a multi-redshift Baryon Acoustic Oscillations (BAO) analysis of the DESI Data Release 2 (DR2) Lyman- alpha (Ly alpha) 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 about2.0 -- 2.5% precision per bin in the radial and transverse directions, corresponding to about1.1 -- 1.2% precision for the isotropic BAO measurement. Using the same data products and modeling framework as the DESI DR2 Ly alpha 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 plus or minus0.39 to 32.22 plus or minus0.47 and in the Alcock-Paczy'nski parameter D M/D H from 3.96 plus or minus0.15 to 5.63+0.22-0.24. The Hubble distance D H/r d decreases from 9.40 plus or minus0.20 to 7.22 plus or minus0.17, providing a direct measurement of the expansion history consistent with CDM and the expected matter-dominated scaling, with H(z) proportional to(1+z) n giving n=1.34 plus or minus0.16. The redshift split also provides a self-consistent measurement of clustering evolution: the Ly alpha forest bias evolves as (1+z) gamma with gamma alpha=3.05 plus or minus0.16, the RSD parameter has a redshift evolution described by gamma beta=-0.97 plus or minus0.26, and the quasar bias evolves with gamma Q=1.56 plus or minus0.23, 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 Ly alpha BAO analysis in flat CDM and w 0w a CDM and improves curvature constraints by about12% in CDM + K.

Sources

Related papers