Large imaging surveys for cosmology: cosmic magnification and photometric calibration

Abstract

This thesis work focuses on the use of deep, wide field surveys to extract new cosmological information. Precise photometry plays a large role in this quest, through the determination of photometric redshifts and the propagation of photometric errors into the cosmological results. This is a unifying theme which effectively ties both parts of the thesis together. After a general review of cosmology and the measurements that support the ΛCDM model, and a description of the Large Synoptic Survey Telescope (LSST), the first part of this work deals with the influence of the variation of main atmospheric constituents on ground-based photometry, focusing particularly on the LSST site at Cerro Pachon, Chile. We process all recent available data on ozone, water vapor and aerosols to construct a long-term atmospheric simulation and estimate quantitatively how the spatial and temporal gradients of these constituents would affect LSST calibration process. The second part of this work starts with a theoretical description of gravitational lensing, concentrating on the weak lensing aspect. After discussing the advantages and difficulties of cosmic shear measurements, we explore the use of cosmic magnification, together with the redshift tomography enabled by the LSST, to constrain cosmological models. We find that cosmic magnification covariance is beset by intrinsic clustering but nevertheless represents a useful probe of galaxy bias and dark energy that complements cosmic shear, and which can increase the robustness of cosmological constraints from lensing surveys.