Séminaire Univers / 
« Lifting weak lensing degeneracies with a fieldbased likelihood » 
Natalia Porqueres 
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 twopoint statistics that, unavoidably, lose information. I will present a fieldbased approach, called BORGWL, that jointly infers the cosmological parameters and the dark matter distribution. BORGWL uses a physical description of gravity to link the primordial fluctuations to the evolved matter density. Its sensitivity to the cosmology is threefold: through the initial matter power spectrum, the growth of structures, and the geometry via the distanceredshift relation. This fieldbased 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, BORGWL yielded marginal uncertainties on sigma8 and Omega_m that are, respectively, a factor of 3 and 5 smaller than those from a twopoint power spectrum analysis on the same data.

mardi 12 octobre 2021  11:15 Webinaire Institut d'Astrophysique de Paris 
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