Exploring the Cosmos with DESI: BAO and RSD measurements
Date:
As the successor to the successful Stage-III BOSS redshift survey and complementing imaging surveys such as DES, CSST, and LSST, DESI embarks on a groundbreaking journey to unravel the properties of dark energy and the evolution of our universe. DESI's planned five-year survey across 14,000 square degrees will target luminous red galaxies (LRGs), [OII] emission line galaxies (ELGs), and quasars, obtaining over 30 million galaxy and quasar redshifts. A large number of redshifts allow the measurement of baryon acoustic oscillations (BAO) with unprecedented precision. Using the initial two months of unblinded data, DESI achieves a 5σ level detection in the LRG sample and a 3σ significance in the BGS sample. Such precision is similar to the final BOSS result after years of operation, demonstrating DESI’s competitiveness as a Stage-IV BAO experiment. DESI's two-point correlation measurements will also detect the anisotropies in galaxy clustering — redshift space distortions (RSD), offering insights into gravity's properties across different epochs. In addition, DESI can also explore neutrino mass, primordial density fluctuations, and potential modified gravity indicators. In this talk, I will first briefly introduce how DESI measures BAO and RSD, highlighting the source of systematic errors; then, I will focus on the DESI Year 1 cosmology results released on April 4, 2024, and their implications.