National Repository of Grey Literature 2 records found  Search took 0.00 seconds. 
Imprint of individual galaxies on gravitational lensing by galaxy clusters
Střeleček, Jan ; Heyrovský, David (advisor) ; Semerák, Oldřich (referee)
The aim of this work is to study gravitational lensing of galaxy-cluster halos in- fluenced by individual galaxies in the halo. The halo mass is generally dominated by dark matter, which can be described using a Navarro, Frenk-White density profile. In our model, we use a spherical halo defined by this model and point masses as simplest approximation for individual galaxies. The analysis of halo-parameter influence on gravi- tational lensing regimes of the combined model yields a complete parameter-space map of critical curves and caustics. In addition we present an adaptation that makes this model numerically more advantageous and we illustrate special cases of the combined influence of two galaxies. 1
Gravitational lensing by combined continuous and discrete matter
Timko, Lukáš ; Heyrovský, David (advisor) ; Semerák, Oldřich (referee)
The aim of this work is to investigate the influence of perturbation by point mass on the caustic structure of the Navarro-Frenk-White model using the inverse ray shooting method. We specifically focus on the description of metamorphoses between different caustic topologies when changing the relative mass and position of the point. It turns out that in the combined model of discrete and continuous matter there appear some types of metamorphoses, such as elliptical umbilic, lips and probably also hyperbolic umbilic, that do not exist in purely discrete models. The main, and somewhat surprising, result of the work is the finding that even at the relative mass of the point 10-4 -10-3 the perturbation is strong enough to cause changes in the caustic structure which are in size comparable to the original caustics.

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