Résumé / Abstract Journal-club_Univers

Journal-club Univers / Journal-club Universe

« Impact of non-linearity on probes combination with future galaxy surveys »

Fabien Lacasa
Dept. Physique Théorique, Univ. Genève (Genève, Suisse)

The success of future galaxy surveys relies on combining probes in order to achieve the tightest possible constraints. However the large scale structure is far from linear and Gaussian as we have been used to when analysing large scales or the CMB. I will show how non-Gaussianity impacts the covariances of each probe of the large scale structure, and more importantly couples them together. Some of these effects are accounted for in current weak lensing surveys, with super-sample covariance (SSC), and I will present the necessary formalism to extend this to future surveys with large sky coverage, where the flat sky approximation can no longer be applied. I will furthermore show that SSC can not be quantified with classical simulations, but it can be predicted analytically with the halo model, or by patching analytical and simulated calculations. Interestingly, cluster counts can be used to mitigate SSC, improving the prospects for extracting cosmological information from small scale weak-lensing or galaxy clustering measurements. Finally, I show that there is a wealth of other non-linear effects which I recently uncovered, that need additional consideration and development as they become important for large and deep surveys such as Euclid and LSST.
mardi 13 mars 2018 - 11:15
Salle 281, Institut d'Astrophysique
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