Séminaires et colloques
[Colloqium] Le projet DESI (Dark Energy Spectroscopic Instrument) : mesure du taux d'expansion de l'univers avec les oscillations acoustiques de baryons. - J. Guy
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Europe/Paris
Grand Amphi (LPSC)
Grand Amphi
LPSC
Description
Baryon Acoustic Oscillations (BAO) are a major probe of the Dark Energy science, with low systematic uncertainties, and an important complementarity with Supernovae Ia for the measurement of the expansion history (absolute distance measurement, measurement of the instantaneous expansion rate, extension of the Hubble diagram to much higher redshifts with the Lyman-alpha forests, measurement of H0 with the inverse distance ladder approach). Massive spectroscopic surveys optimized for BAO can also measure the growth rate of structures with redshift space distortions. This provides an independent test of general relativity on cosmological scales, and helps constraining alternative theories of gravitation designed to explain the recent acceleration of expansion. DESI is a large Dark Energy project optimized for those probes. BAO and redshift space distortions will be measured with LRG, ELG, quasars and Lyman-alpha over a 14,000 square degrees footprint. Observations will be conducted on the 4-m diameter Mayall Telescope at Kitt Peak, Arizona. The survey will begin in 2019 and will last 5 years. DESI will be close to ten times as precise as current BAO surveys, with a combined precision on the radial and longitudinal BAO scales of 0.3% and 0.5% respectively at an effective redshift of z ∼ 1.3. At z > 2.1, with the Lyman-alpha forest auto-correlation, the integrated precision on the radial and longitudinal BAO scale is expected to be of 0.8% and 0.7%. Cross-correlations of Lyman-alpha forests with QSO will provide additional BAO constraints. Much more information will also be provided by the correlation function at smaller scales, at the expense of a more demanding accuracy on the modeling of both the clustering and survey efficiency. For instance DESI will measure the sum of neutrino masses with a statistical uncertainty of 0.020 eV (when considering data up to k max = 0.2 h/Mpc).