Abstract : Type Ia supernovae (SNe Ia) are one of the pillars of modern observational cosmology, since they are good standard candles for distance measurements in the universe. The cosmological analysis using SNe Ia requires the observation of both high and low-redshift objects, and the smaller statistic of events on the latter case represents a major source of uncertainties.
This thesis takes place within the SNfactory project, which aims to study nearby (0.03 < z < 0.08) SNe Ia using an integral field spectrograph, SNIFS. The presented work is divided into: a technical part, dealing with the acquisition, calibration and extraction of data from the SNIFS photometric camera; and an analysis where spectrophotometric light curves issued from SNIFS spectra were obtained, and used to create the first spectrophotometric nearby Hubble diagram.
An extraction pipeline of the differential photometric ratios between nights, needed for the flux calibration of the spectra, was built. The systematic errors affecting these ratios are estimated to be below 2%, and spectrophotometric light curves of standard stars show a 5% photometric precision of the full flux calibration on non-photometric conditions. The obtained nearby Hubble diagram presents a smaller residual scatter than the one made using currently available data. A K-correction free cosmological fit shows an additional reduction of 5% on the scatter, until now undistinguishable from the SNe Ia "intrinsic dispersion".