Interferometry is the ultimate technology for overcoming the limitations which diffraction and the atmosphere-induced seeing impose on the resolution achievable with ground-based telescopes. The latest generation of ...

Dark matter studies in elliptical galaxies were long hampered by the lack of suitable dynamical tracers. The advent of 8 m-class telescopes equipped with multi-object spectrographs has made it possible to use globular ...

The thesis set out to investigate the nature and genesis of the peculiar class of X-shaped radio galaxies. X-shaped sources are puzzling because of the extremely low number of objects of that type. Three scenarios were ...

Pulsars are highly magnetised neutron stars which spin tremendously fast, at periods that are as low as a few milliseconds. Chapter 1 gives an overview of their basic observational properties and applications. Pulsars are ...

The physics and chemistry of the circumstellar envelopes (CSEs) of evolved stars are not fully understood despite decades of research. This thesis addresses two issues in the study of the CSEs of oxygen-rich (O-rich) evolved ......

We perform a cosmic shear analysis of 15 square degree high-quality R-band data of the Garching-Bonn Deep Survey (GaBoDS) obtained with the Wide-Field-Imager (WFI) at the ESO/MPG 2.2m telescope. The GaBoDS comprises 1.75 ...

Massive stars play an important role in shaping the structure of galaxies due to the large energy output during their lifetime. However, because of the short evolutionary time scales, the large extinction toward their birth ...

Systematic surveys of the extra-galactic sky have revealed the existence of large-scale structures in the Universe: the galaxy distribution is organized in a complex network of filaments surrounding underdense regions and ...

Galaxies with H₂O-megamaser-disks are low luminosity active galaxies where 22GHz H₂O-maser emission is detected in their accretion disk surrounding the central supermassive black hole (SMBH). Furthermore, ...

Massive star evolution taking place in astrophysical environments consisting almost entirely of hydrogen and helium – in other words, low-metallicity environments – is responsible for some of the most intriguing and energetic ...