Study of the diverse components of the polarized sky in preparation to the Cosmic Microwave Background with the Planck satellite

This thesis is dedicated to the measurement of the Cosmic Microwave Background (CMB) anisotropies and to the characterization of its Galactic foregrounds. This work has been done in the framework of the Planck satellite data analysis preparation. First, a general introduction to cosmology and to CMB is presented. An overview of the current cosmological measurements is given and the Archeops, WMAP and Planck experiments are introduced. Part two is devoted to the effect of a primordial magnetic field on CMB polarization. We derive the angular power spectra of this effect and give a superior limit on the nowadays intensity of this field using the WMAP data. In a third part, we present the analysis we have performed using the Archeops data. First, we show the Gaussian nature of the temperature data measured at 143 GHz, constraining the nonlinear coupling factor and systematic residuals and then, using the polarized data from the 353 GHz channel, we show the first measurement of the polarized diffuse emission of dust at large angular scales. In a fourth part, we present an original component separation method allowing to extract the various physical contributions from multi-frequency observations, in both temperature and polarization. Performances of the method are intensively tested using Planck sky simulations. Finally, we focus on the modelization of the polarized Galactic emissions of synchrotron and dust and we compare our simulations of these emissions to the Archeops and WMAP polarized data. (author)