During his PhD at CEA Saclay, Arnaud de Mattia performed a clustering analysis of the Emission Line Galaxy (ELG) sample from the eBOSS program of the SDSS. His work included a detailed study of the impact of survey geometry and observational systematics on clustering measurements.
After his PhD, Arnaud joined the Dark Energy Spectroscopic Instrument (DESI) collaboration, where he has worked successively on photometric systematics (through image simulations), clustering catalogs and two-point statistics, and cosmological parameter inference. He is deeply involved in pipeline development for DESI — from catalog creation to cosmological constraints — leveraging GPU computing and automatic differentiation whenever relevant.
Arnaud co-chaired (2022–2024) the DESI Cosmological Parameter Estimation Working Group, responsible for BAO and Full-Shape cosmological constraints from DESI DR1 data, and since 2025 he has been co-chairing the Galaxy and Quasar Clustering Working Group. In parallel to the standard analyses, Arnaud is also interested in galaxy field-level inference as a more comprehensive approach to cosmological analysis.
Title: DESI DR2: Survey Overview, Cosmological Constraints from BAO, and Preparation for Full-Shape Analyses
Abstract: The Dark Energy Spectroscopic Instrument (DESI) is conducting a groundbreaking survey designed to measure over 40 million extragalactic redshifts across 14,000 square degrees of the sky over its nominal five-year program — recently extended to eight years. These observations aim to refine our understanding of the Universe’s expansion history through Baryon Acoustic Oscillations (BAO) and to probe the growth of cosmic structure via Full-Shape analyses.
In 2025, the DESI collaboration released its BAO cosmology results from Data Release 2 (DR2), based on the first three years of observations (2021–2024). This presentation will provide an overview of the survey, summarize the BAO measurements and corresponding cosmological constraints from DR2, and highlight ongoing efforts within DESI to prepare for Full-Shape analyses, including work on higher-order three-point statistics. I will also present ongoing research in my group on field-level inference, which aims to extract cosmological information directly from the galaxy density field.