On the inversion methods of strong gravitational lensing

In dieser Dissertation präsentiere ich eine neue Methode zur Inversion der Linsengleichung. Der präsentierte Algorithmus basiert auf dem Modifizierten Hausdorff- Abstand zwischen beobachteten und modell- erzeugten Bögen als eine Funktion der Fit-Güte. Die Minimierung dieser Funktion der Fit-Güte hat sich als sehr erfolgreich zur Auffindung des Linsenpotentials herausgestellt, da sie relativ einfach zu berechnen ist und die volle Information nicht nur der Bogenpositionen sondern auch ihrer Form enthält. WeitereMinimierungs- Schemata, darunter Powell, Markov ChainMonte Carlo und Genetische Algorithmen, werden untersucht, und es wird gezeigt, dasz sie kombiniert die besten Resultate liefern. Die entwickelte Methode wird mit groszem Erfolg auf den Starklinsen-Galaxienhaufen RCS0224-0002 angewandt. Das resultierende Modell ist in der Lage, alle beobachteten Starklinsen-Eigenschaften dieses Haufens im Detail wiederzugeben, be- vorzugt das NIS radiale Profil gegenueber NFW und sagt eine verbl üffende Verschiebung um fuenf Bogensekunden zwischen dem Massenschwerpunkt und dem Zentrum der Roentgenemission voraus. Zum Abschlusz wird die Doku- mentation des Softwarepakets (C++ und IDL) zur Implementierung der Inversionsmethode präsentiert

Strong Lensing Analysis of the Cluster RCS0224-0002 at z=0.77z=0.77

We present a detailed mass reconstruction of the cluster RCS0224-0002 at $z=0.773$ from the strong lensing features observed with HST/WFPC2. The mass profile is reconstructed using a parametric approach. We introduce a novel method to fit extended multiple images based on the Modified Hausdorff Distance between observed arcs and the arcs reproduced by the model. We perform the detailed error analysis of the model parameter using the MCMC method. Our model reproduces all the observed strong lensing features of the RCS0224-0002 and predicts the redshift of one of the arcs systems to be $z\approx 2.65$ (the other system has an spectroscopic redshift of $z=4.87$). The reconstructed inner mass profile is well fitted by a non-singular isothermal sphere, rather than with an NFW model. Dark matter substructure, derived from the light distribution of the most luminous cluster members, is crucial for reproducing the complexity of the quadrupole image system, which could not be achieved otherwise. The reconstructed mass distribution closely follows the light, however it is significantly shifted from the X-ray emission of the gas. The mass of RCS0224-0002 derived from the lensing model, $\approx 2\times10^{14} M_\odot$ is in a very good agreement with the one obtained from the X-ray temperature measured with deep Chandra observations.Comment: 13 pages, accepted for A&

Effects of zebra mussels on cladoceran communities under eutrophic conditions

The purpose of this study was to determine how zebra mussels affected cladoceran community structure under eutrophic conditions. We conducted a mesocosm study where we manipulated the presence of zebra mussels and the presence of large-bodied Daphnia (Daphnia magna and Daphnia pulicaria). We also conducted a complimentary life-table experiment to determine how water from the zebra mussel treatment affected the life history characteristics of the cladoceran species. We anticipated that small- and large-bodied cladoceran species would respond differently to changes in algal quality and quantity under the effects of zebra mussels. Large-bodied Daphnia successfully established in the zebra mussel treatment but failed to grow in the control. We did not observe positive relationships between food concentrations and cladoceran abundances. However, the phosphorus content in the seston indicated that food quality was below the threshold level for large-bodied cladocerans at the beginning of the experiment. We believe that zebra mussels quickly enhanced the phosphorus content in the seston due to the excretion of inorganic phosphorus, thus facilitating the development of large-bodied Daphnia. In conclusion, our results suggest that zebra mussels can alter the phosphorus content of seston in lakes and this can affect the dynamics of crustacean zooplankton

The management and survival outcomes of nasopharyngeal cancer in the Nordic countries

Peer reviewe