BAO and Lyman-Alpha forest results from the DESI survey

by Dr Hiram Herrera-Alcantar (CEA)

Tuesday May 20, 2025, 11:00 AM → 12:00 PM Europe/Paris

Salle du conseil (IAP)

The Dark Energy Spectroscopic Instrument (DESI) survey is mapping over a 14000 square degrees footprint and will obtain spectra and precise redshifts for more than 40 million galaxies and quasars. In its second data release (DESI-DR2), we present baryon acoustic oscillation (BAO) measurements from over 14 million galaxies alongside a Lyman-α (Lyα) forest sample drawn from 820 000 quasars at z > 2.1. A combined analysis of the DR2 galaxy and quasar samples strengthens earlier hints of dynamical dark energy detected in DR1.
In this talk, I will first present our latest BAO results and their cosmological interpretation. Then, I will focus on the Lyα forest, where I will briefly review its physical basis, and describe the DESI-DR2 Lyα clustering analysis pipeline, its validation, and our measurement of the BAO scale at effective redshift z_eff=2.3, with 1.1% precision along the line of sight and 1.3% across it. Finally, I will present preliminary results on the Lyman-Alpha forest extracted from Lyman Break Galaxy (LBG) spectra measured by DESI pilot surveys, demonstrating their promise for extending precise cosmological constraints to redshifts beyond those achievable by quasars.