Gravitační čočkování substrukturami v halech temné hmoty

Karamazov, Michal

Gravitational lensing serves as an invaluable tool for studying the distribution of mat- ter in the universe. This matter is predominantly dark and clumped into centrally concen- trated hierarchically structured halos of galaxies and galaxy clusters. Early comparisons suggested discrepancies between the high population of substructures predicted by cos- mological simulations and the lack of corresponding observational data. More recently, a major discrepancy in the opposite sense was reported from analyses of lensing galaxy clusters: the lensing efficiency of their substructures was found to be much higher than predictions based on cosmological simulations. In this thesis, we examine gravitational lensing by substructures embedded in dark-matter halos with Navarro-Frenk-White (NFW) density profiles. We start by a detailed investigation of a simple model with a single point mass perturbing the halo. Using analytical methods, we study its critical curves, caustics and their transitions. Next, we explore the geometry of lensed images and the weak-lensing characteristics of the same simple model, developing novel ways of their visualization. Finally, we construct a more realistic lens model of a galaxy cluster con- sisting of an ellipsoidal cluster halo combined with a population of truncated ellipsoidal galaxy...

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