Abstract. The recent detections of cosmic shear signal announced by several groups have demonstrated the feasibility of this challenging program and convinced astronomers of its potential for cosmology. Cosmic shear analysis demands to handle Gigabytes of data in order to probe several square degrees in subarcsecond deep imaging mode. The success of these surveys is sensitive to the designs of the observation strategy, the organization of the data reduction pipelines and the links of the data base with surveys like X-ray or spectroscopic follow up. We describe the cosmic shear surveys we have carried out at the VLT and at CFHT and the way we handle this huge data set in a more general context including the VIRMOS and the XMM-LSS surveys, and the future CMB surveys.
Cosmology with weak lensingLarge-scale structures of the universe induce gravitational lensing effects which accumulate on photons emitted by distane sources. On deep CCD images, they revealed themselves as a weak modification of the shape of galaxies which adds to their intrinsic ellipticity to produce a cosmological shear signal, called the cosmic shear. The light beam deformation witnesses the history of mass density fluctuations from the emitting (lensed) sources to the observer. Therefore, it is a signature of the cosmological scenario of structure formation and its study should provide interesting clues on several cosmological quantities, like the cosmological parameters, the power spectrum of density fluctuations and the biasing 1 .
Gravitational weak shear produced by large-scale structures of the universe induces a correlated ellipticity distribution of distant galaxies. The amplitude and evolution with angular scale of the signal depend on cosmological models and can be inverted in order to constrain the power spectrum and the cosmological parameters. We present our recent analysis of 50 uncorrelated VLT fields and the very first constrains on (Ωm, σ8) and the nature of primordial fluctuations based on the join analysis of present-day cosmic shear surveys.
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