Weak Lensing Detection And Analysis Of Galaxy Clusters In CFHT And VST Surveys

This thesis discusses weak gravitational lensing as a method to obtain a complete census of galaxy clusters, the most massive cosmic systems, with mass up to～1015M and to calibrate their empirical scaling relations. Galaxy clusters are important cosmo-logical probes, as their mass function is a sensible function of the cosmological param-eters. Weak gravitational lensing offers the unique possibility of a robust measurement of galaxy clusters mass, regardless any assumption about their dynamical state or mass composition.This technique requires wide and deep surveys of the sky (i.e., several hundreds of square degrees) in order to be effective and with results comparable with more traditional ones. First effective weak lensing surveys of galaxy clusters have been possible only recently,, with the advent of wide field detectors on4m-class telescopes.In October2011, a new, promising survey machine, the VLT Survey Telescope, has started its scientific operations. Two complementary surveys are aim at the detection of weak lensing phenomena by galaxy clusters, the wide and shallow survey KiDS (Kilo Degree Survey) covering1500square degrees, and the deep survey VOICE (VST Optical Imaging of the CDFS and ES1Fields), over8square degrees.The goal of this Thesis is twofold. First we aim at using the weak lensing pipeline developed in our team to build a catalog of mass-selected galaxy clusters and study their scaling relations at intermediate redshift, by using well characterized data from the Canada France Hawaii Telescope. Second, we use recent data from the VST in order to test its performance as a weak lensing machine, effort done here for the first time.