Orateur
Description
The Dark Energy Spectroscopic Instrument (DESI) is building the largest 3D map of our universe to measure its expansion history over the past 11 billion years, and thereby, study dark energy. Over a five-year period (Run 1a), DESI has spectroscopically classified nearly 40 million galaxies and quasars over 1/3 of the sky and to redshifts z < 3.5.
The DESI collaboration has completed measurements of the baryon acoustic oscillation (BAO) feature and more generally, of large-scale structure, using data from the first three years of observation (DR2). In this seminar, I will present those measurements and their implications for our understanding of the cosmological model, I will discuss the tensions with LambdaCDM and the question of the nature of dark energy.
I will also present new results from DR2 on the Lyman-alpha forest of quasars. First, a full-shape analysis of the Lyman-alpha forest power spectrum, providing a measurement of the Alcock-Paczyński effect at high redshift (2 < z < 3). Second, a new multi-redshift BAO analysis of the Lyman-alpha forest splitting the data into three redshift bins, probing the matter-dominated expansion at the highest redshifts accessible to DESI.
Finally, I will give a brief outlook on the future of the DESI program. Run 1b, which follows Run 1, extends the survey with an increased tracer density and an enlarged footprint towards the southern sky. Looking further ahead, DESI Run 2 is scheduled to begin in 2029 and will span seven years, targeting the primordial universe at z > 2 and opening a new window on the early-time expansion history and primordial physics.