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Probing the matter distribution on intermediate and large scales with weak light deflections
Gravitational lensing can constrain the cosmic density field, its evolution and spacetime geometry. In the first part of this dissertation I demonstrate how information about the internal structure of galaxy clusters can be gained from observations of weak gravitational lensing. I present a novel approach which does not rely on symmetry assumptions or parametric models, but is instead built on a translation-invariant geometric description using Minkowski functionals. An integral measure of the convergence is constructed from the shear field. The behaviour of excursion sets of this estimator for varying thresholds characterises the morphology of the mass distribution. An intrinsic scale in the density profile manifests itself in a change of the logarithmic slope of the first Minkowski functional. I show how the characteristic noise profile of the density estimator affects the measurement and develop a strategy which permits the discrimination between a scale-rich profile and a power law. In the second part I study cross-correlations between weak lensing and the integrated Sachs-Wolfe effect. I treat cosmic shear as a three-dimensional observable and develop a formalism in which the covariance of both signals can be calculated. For the numerical evaluation a highly efficient method was implemented, the performance and reliability of which I demonstrate in a Fisher analysis. For a data set of the quality of upcoming survey missions like the Euclid satellite, taking the cross-correlation between the two signals into account lowers the error on cosmological parameters by ten per cent.
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530 Physik
530 Physics