Radio galaxies and the intergalactic medium

We are studying radio galaxies and distant extra- galactic radio sources in various environments in order to shed light on the physics intrinsic to these objects, while also learning more about their sur- rounding (intergalactic) medium. The main topics addressed by these investigations are:
Lifetimes of radio galaxies
Diagnostics of the IGM
Source statistics
A review article comprising the various aspects of radio galaxy research may be found here (in Ger- man).
















    We have several on-going projects based on observations with the following telescopes:
One of the first projects has been a thorough study of giant radio galaxies, the largest such objects known in the universe. In the framework of his P.D. thesis, Karl-Heinz Mack (CNR Bologna) made the first analysis of GRGs over large frequency range (327 MHz - 10.6 GHz) using the 100-m te- lescope and the WSRT, involving all Stokes parameters. Here you can enjoy a potpourri of images showing the record holder in size, 2C236, which measures some 4.5 Mpc across (H0 = 75 km s-1).
The total intensity is represented by contours, with the polarization superimposed as vectors, their lengths being proportional to the polarized intens- ity, and their orientations indicated the projected magnetic field (note that Faraday rotation works at frequencies below about 5 GHz). If you are in- terested in performing a DIPLOMARBEIT in this field of research, we still have some interesting multi-frequency data waiting for reduction and analysis...!



    On-going research:

Radio source asymmetries, Faraday rotation and the density of the IGM
      This is the subject of Bong Won Sohn's Ph.D. thesis. He started of by investigating
      the possible nature of morphological and spectral asymmetries in radio galaxies. In the       course of his studies, he had a closer look at rotation measures of extended sources,
      from which he developed interesting ideas about the density of the IGM.
The formation of jets in X-shaped radio galaxies
      This particular species of radio galaxies is the subject of Helge Rottmann's Ph.D.
      thesis. Helge has also been working on the large-scale structure, polarization and
      spectral index of the peculiar radio galaxy Vir A. Click here for a review on this topic.
Study of the extreme ultraviolet emission from clusters of galaxies
      This is the subject of Abouzar Najafi's Diplomarbeit, in which he tries to interpret the       excess extreme-ultraviolet emission from the Coma Cluster of Galaxies by a non-
      thermal model, considering both hadronic and leptonic processes in the intra-cluster
      matter.
More studies of galaxy clusters and the IGM
      This is a collaboration with Peter Biermann, Michael Thierbach, Torsten Enßlin,
      Richard Wielebinski. Michael has observed galaxy clusters at high frequencies using
      the 100-m telescope. His spectral and polarization analysis not only provides valuable       zero-spacing data for interferometric measurements, but also confirms our current
      comprehension of the nature of radio halos and relic sources in clusters (see his Ph.D.       work).
Effelsberg observations of B3/VLA sources
      We are studying a large sample of radio sources from the so-called B3/VLA survey.
      This project, in which we study the high-frequency continuum spectrum of these
      sources, is a collaboration with Mario Vigotti, Loretta Gregorini & Karl-Heinz Mack
      CNR Bologna.