Projects

Dwarf Galaxies

Dwarf galaxies form the low mass end of galaxies. They populate the environment of larger galaxies as well as the intergalactic space of the Local Group of Galaxies. The large and the small Magellanic Cloud represent the best known dwarf galaxies belonging to the Milky Way galaxy. From the Earth's southern hemisphere, they can be seen with the naked eye.

We can differentiate roughly between two different classes of dwarf galaxies: dwarf spheroidals and dwarf irregulars. Dwarf spheroidals appear as globular star-cluster like objects, while dwarf irregular galaxies represent the gas rich population with on-going star-formation.

Our research interest is focussed on the dwarf irregular galaxies. Using XMM-Newton and Chandra X-ray data we study the population of energetic objects within these dwarf galaxies. Their frequency of occurrence is a measure for the star-formation activity of the galaxies. Moreover, we search for the diffuse X-ray emission associated with individual HI-holes and -shells as well as for extended emission enclosing the whole galaxy.

For further details please visit the dwarf galaxies page or contact Meikel Kappes or Jürgen Kerp.

This research is supported by the Deutsches Zentrum für Luft- und Raumfahrt under grant No. 50 OR 0103.

The Magellanic Clouds

The Magellanic Clouds form a spectacular set of galaxies at the southern hemisphere. Detailed radio astronomical observations of the HI emission reveal the existence of a huge coherent gas stream across half of the sky. Using the Parkes 21-cm multi-feed receiver system Christian Brüns headed the scientific program to map the whole gas stream called the Magellanic Stream. Within his Ph. D. thesis he compiled a complete flux-limited catalogue of all gas clouds belonging to the Magellanic Stream and performed detailed studies of the physical and chemical composition of the gas within the stream.

For further information please visit the Magellanic Clouds page or contact Christian Brüns.

The Soft X-Ray Background

Since soft X-rays (0.2 - 2 keV) from space are totally absorbed by the Earth's atmosphere, one needs balloons or satellite observatories in high altitude orbits to study X-rays from space. The particular interest of our group is the soft X-ray background observation, performed with satellites like XMM-Newton and ROSAT. Because this diffuse soft X-ray emission is observable across the whole sky, we denote this radiation as "background" emission, but this does not imply a physical origin beyond the Milky Way as for example the cosmic microwave background.

The study of the soft X-ray background allows to "X-ray" gaseous clouds of the Milky Way in a manner comparable to the medical applications of the X-rays. Using this technique it is possible to determine the density and chemical composition of clouds in front of the diffuse X-ray background. Studying the relative distance to Milky Way gas clouds allows to constrain the 3-D structure of X-ray emitting and absorbing regions. Combined with supplementary radio astronomical and optical data, we can produce realistic models of the Galactic X-ray Halo, and of the X-ray environment of the Sun.

For further information please visit the soft X-ray background page or contact Juan Pradas or Jürgen Kerp.

This research is supported by the Deutsches Zentrum für Luft- und Raumfahrt under grant No. 50 OR 0103.

Radio Galaxies in X-Rays

Radio galaxies form the upper mass and size end of all galaxies in the Universe. They are most frequently embedded within a group of galaxies or a cluster of galaxies. Their host galaxies are elliptically ones. The term radio galaxy denotes the fact that these galaxies are prominent at radio wavelengths. Most prominent are the jets and huge radio lobes which can reach the extent of several times the linear extent of the Milky Way Galaxy.

We focus on the X-ray emission of radio galaxies. Using XMM-Newton and Chandra data, we study the diffuse X-ray emission of the host galaxy as well as the X-ray jet. The aim of our research project is to identify the emission process of the observed X-ray photons which appears to be directly linked to the activity of the active galactic nucleus in the very centre of the radio galaxy.

For further information please visit the radio galaxies page or contact Matthias Kadler or Jürgen Kerp.

The Milky Way Galaxy in HI

The Milky Way is the closest galaxy that can be studied. Unfortunately or better fortunately we are located within this galaxy. This special location allows to study each region in great detail and with high quality data but also in such a detail that makes it difficult to differentiate between major and minor details of each individual object.

We are mainly interested in the HI 21-cm line distribution of the Milky Way. The first whole sky HI survey - covering the northern and the southern galactic sky - is in its final state of data reduction. Using this unique survey a wealth of information on the physical conditions of the Milky Way and its Halo is accessible.

For further information please visit the Milky Way page or contact Peter Kalberla.

High-Velocity Clouds

We denote gaseous clouds as High-Velocity Clouds (HVCs) if their observed velocities are inconsistent with the rotation of the Milky Way. HVCs do not only show "strange" velocities, but also an unusual chemical composition. Today we can roughly differentiate between two types of HVCs: the classical ones which are located within the environment of the Milky Way Halo, and the compact HVCs (CHVCs) which are thought to represent gaseous debris or residuals from the formation of the Local Group galaxies. This cosmological context makes CHVCs extremely attractive for the current research, despite of the fact that these clouds are only observable in a single element, the neutral atomic hydrogen HI.

For further information please visit the High-Velocity Clouds page or contact Tobias Westmeier, Christian Brüns, or Jürgen Kerp.

This research is supported by the Deutsche Forschungsgemeinschaft under grant No. Ke 757/4-1