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oai:recercat.cat:2117/4495602026-01-19T02:55:18Zcom_2072_1033col_2072_452950

DESI DR2 results. I. Baryon acoustic oscillations from the Lyman alpha forest Abdul Karim, Marie Lynn Aguilar, Jessica Nicole Ahlen, Steven Allende Prieto, Carlos Alves, Otávio Anand, Abhijeet Andrade, Uendert Armengaud, Eric Avilés, Alejandro Pérez Ràfols, Ignasi Universitat Politècnica de Catalunya. Departament de Física Universitat Politècnica de Catalunya. GAA - Grup d'Astronomia i Astrofísica Àrees temàtiques de la UPC::Física::Astronomia i astrofísica Baryon acoustic oscillations Dark energy Large scale structure of the Universe We present the baryon acoustic oscillation (BAO) measurements with the Lyman-¿ (Ly¿¿ ) forest from the second data release (DR2) of the Dark Energy Spectroscopic Instrument (DESI) survey. Our BAO measurements include both the autocorrelation of the Ly¿¿ 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 2 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 Ly¿¿ 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 ¿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 Ly¿¿ BAO analysis for the first time. We measure the ratios ¿¿¿(¿eff)/¿¿ =8.632 ±0.098 ±0.026 and ¿¿¿(¿eff)/¿¿ =38.99 ±0.52 ±0.12 , where ¿¿ =¿/¿¿(¿) is the Hubble distance, ¿¿ is the transverse comoving distance, ¿¿ 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. Peer Reviewed Postprint (published version) 2025-10-06 Article Abdul, M. [et al.]. DESI DR2 results. I. Baryon acoustic oscillations from the Lyman alpha forest. «Physical review D», 6 Octubre 2025, vol. 112, núm. article 083514, p. 1-28. 2470-0010 https://hdl.handle.net/2117/449560 10.1103/2wwn-xjm5 eng https://journals.aps.org/prd/abstract/10.1103/2wwn-xjm5 http://creativecommons.org/licenses/by/4.0/ Open Access Attribution 4.0 International 28 p. application/pdf American Physical Society (APS)