Extragalactic Astronomy

At MPE the study of extragalactic objects and structures was primarily initiated by the ROSAT mission. It still relies to a large extent on X-ray data obtained from the ROSAT satellite and, later on, from the Japanese ASCA and the American RXTE satellites.

More recently, the emphasis of our activities has been shifted towards the theoretical interpretation and numerical modelling of the systems. However, the new large X-ray missions Chandra and XMM started to provide data of unprecedented quality which will drive a completely new era of extragalactic research.

Our research activities in Extragalactic Astronomy basically cover two main fields:

AGN

Active Galactic Nuclei (AGN) are galaxies in which the energy output from the central nucleus exceeds the bolometric luminosity of the stellar population by several orders of magnitude. As a substantial fraction of this luminosity is emitted at higher energies X-ray observations provide the best tool for a study of the physical conditions of the central engine of these objects.

Clusters and Large Scale Structures

Clusters of galaxies are luminous X-ray sources due to X-ray emission from hot intergalatic plasma at temperatures of several million degrees. The study of X-ray images and spectra of clusters provides important information on the structure, mass, composition, and physics of these galaxy systems. Based mainly on ROSAT and ASCA observations we have studied a wide range of astrophysical phenomena in clusters.

The structure and spatial distribution of clusters is also closely linked to the structure of the Universe as a whole. The study of the population of galaxy clusters gives therefore an interesting insight into the large-scale structure and evolution of our Universe. Since clusters are clearly indentifiable through their X-ray emission, we are exploiting the unique opportunity offered by the ROSAT All-Sky X-ray Survey to survey the sky for the X-ray brightest clusters to conduct several important cosmological studies.