Active Galactic Nuclei (AGN) are known to show significant flux density variability across the whole electromagnetic spectrum on a wide range of time scales, from years to less than one day. In the radio regime, variability ...

While searching sets of discrete data contaminated heavily by noise for weak signals of correlated data points we have made use of statistic quantities to detect correlations between data points. The signal consists of ...

Since 1997 the Bonn University Institute of Physics operates a Rayleigh/Mie/Raman lidar on the Esrange near the Swedish city of Kiruna north of the Arctic circle. During seven winter and six summer campaigns a large amount ...

The main goal of this thesis is to investigate the dark matter halos of galaxies. Current theories of galaxy formation predict that galaxies are embedded in large dark matter halos with much larger extents than the visible ...

The close connection between bars and box/peanut-shaped bulges is observationally and theoretically supported. However, for the class of thick box/peanut-shaped bulges an environmental hypothesis instead of an internal ...

In this work, we have studied the asymmetries of radio galaxies which are known to be related to the jet-asymmetry. They are the depolarization asymmetry and the spectral index asymmetry. <br /> The first part of the thesis ...

Tau lepton decays with open strangeness in the final state are measured with the OPAL detector at LEP to determine the strange hadronic spectral function of the t lepton and the mass of the strange quark. The decays ...

The deflection and distortion of a light bundle by tidal gravitational fields is described in the framework of General Relativity. There, light bundles from a source follow exactly the curvature of spacetime, and are ...

In this thesis, the proper motions of two Local Group galaxies, namely M33 and IC10. The proper motions were measured by phase-referencing Very Long Baseline Interferometry (VLBI) observations of water vapour masers in the ...

The Cassini/Huygens mission to Saturn, a joint venture of NASA and ESA, was launched on 15 October 1997 from Kennedy Space Center, Cape Canevaral, Florida (USA) and will reach its destination in July 2004. The Huygens Probe ...