Institute for Astrophysics and Geophysics

Active and Normal Galaxies

Normal galaxies consist of about 100 billion stars, as well as gas and dust. Galaxies evolve on cosmological timescales with respect to their morphology, stellar composition and age, gaseous content and chemical composition. Massive black holes, a billion times more massive than our sun, are presumed to reside in the center of every galaxy in the Universe. Active Galactic Nuclei (AGN) around these black holes enable us to study the physics of their close environment and to measure their mass. The activity is connected with feeding of fresh gas from the outskirts of the galaxy into the central black hole. This feeding might be caused by tidal interactions of moving galaxies. Active Galactic Nuclei are the most powerful light sources in the Universe. We are investigating with 1dim. and 2dim. spectroscopy, multifrequency observations (optical, UV, radio, X-ray), as well as by comparison with model calculations the following topics:



Research Interests


  • Physical processes in Active Galactic Nuclei: Structure, Velocity Fields in AGN Nuclei, Supermassive Black Holes, Spectral Variability of AGN, Multi-Frequency Observations (X-UV-Opt-IR-Radio), Spectropolarimetry
  • (AGN) Host Galaxies: Morphology, Internal Velocity Fields, Starburst Activity, Stellar Population/Evolutionary Synthesis
  • Environment of Active Galaxies: Merging Galaxies, Interacting Galaxies, Groups/Clusters of Galaxies, Large Scale Structures



Inner Region of AGN

Fig.1: Artist’s impression of the innermost region in AGN. A disk of hot gas is surrounding the central black hole. Two jets of high energy particles are propelled away from the vicinity of the black hole (NASA).



interacting galaxies

Fig.2: The interacting galaxies NGC5426-5427 (Gemini observatory).




[1] Kollatschny, W.; Zetzl, M.: Broad-line active galactic nuclei rotate faster than narrow-line ones, 2011, Nature 470, 366
[2] Frieman, J.; ...; Kollatschny, W.: The Sloan Digital Sky Survey-II Supernova Survey: Technical Summary, 2008, AJ 135, 338
[3] Kollatschny, W.: Spin orientation of supermassive black holes in active galaxies, 2003, A&A 412, L61
[4] Kollatschny, W.: Accretion disk wind in the AGN broad-line region: Spectroscopically resolved line profile variations in Mrk 110, 2003, A&A 407, 461
[5] Kollatschny, W.; Bischoff, K.; Robinson, E. L.; Welsh, W. F.; Hill, G. J.: Short-term emission line and continuum variations in Mrk 110, 2001, A&A 379, 125
[6] Kollatschny, W.; Kowatsch, P.: The X-ray jet in the merging galaxy system Markarian 266, 1998, A&A 336, L21