Résumé / Abstract Journal-club_Univers

Séminaire Univers /
Seminar Universe

« Lifting weak lensing degeneracies with a field-based likelihood  »

Natalia Porqueres
Department of Physics, Imperial College (Londres, Royaume-Uni)

With Euclid and the Rubin Telescope starting their weak lensing measurements in the coming years, we need data analysis techniques that optimally extract the information from the data rather than relying on two-point statistics that, unavoidably, lose information. I will present a field-based approach, called BORG-WL, that jointly infers the cosmological parameters and the dark matter distribution. BORG-WL uses a physical description of gravity to link the primordial fluctuations to the evolved matter density. Its sensitivity to the cosmology is three-fold: through the initial matter power spectrum, the growth of structures, and the geometry via the distance-redshift relation. This field-based approach lifts the strong degeneracy between the matter density (Omega_m) and the fluctuation amplitude (sigma8), providing tight constraints on these parameters from weak lensing data alone. In an experiment with simulated data, BORG-WL yielded marginal uncertainties on sigma8 and Omega_m that are, respectively, a factor of 3 and 5 smaller than those from a two-point power spectrum analysis on the same data.
mardi 12 octobre 2021 - 11:15
Institut d'Astrophysique de Paris
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