Guest Astronomy - Prof. Dettmar


28.04.2017 - Dr. Andrew Fletcher

Dr. Andrew Fletcher from the Newcastle University, UK, stayed at the research group for Astronomy of Prof. Dettmar for four weeks. He started his visit on April 18th and left at May 15th, 2017. In this time he collaborated with the people from Bochum on magnetic fields.

A highlight of his stay was the seminar talk with the title "Magnetic field in the multi-phase interstellar medium" on May 4th, 2017.

Abstract: I will review what is known about the general properties of magnetic fields in the diffuse interstellar medium. New results will then be presented, addressing questions such as:
is the mean, large-scale, magnetic field preferentially connected to a particular phase of the ISM? what effect does the generation of the mean-field have on ISM structure? what are the space and time correlations of random fluctuations in the ISM? how are these correlation scales related to observables?


31.10.2016 - Prof. Dr. Judith Irwin

In der Zeit von September bis November 2016 besuchte Prof. Dr. Judith Irwin von der Queen’s University in Kingston, Kanada den Lehrstuhl für Astronomie von Prof. Dettmar. Im Rahmen dessen hielt sie einen Kolloquiums-Vortrag.

Title: Radio Circular Polarization in the Nuclei of Nearby Galaxies 

Abstract: Circular polarization is technically difficult to measure in astrophysics, due to the weakness of the signal. Very few sources have had confirmed circularly polarized signals, but the scientific payoff can be significant, especially the potential insight that such observations provide on the nature of Active Galactic Nuclei.

This talk will review observations of circular polarization in nearby systems, as well as present some new results from CHANG-ES (Continuum Halos in Nearby Galaxies -- an EVLA Survey). A close look at circular polarization is especially timely now that we are approaching the era of the Square Kilometre Array. 

link to Kolloquium RUB Physik

Beide arbeiten zusammen in dem CHANG-ES Projekt, das folgende wissenschaftliche Zielsetzung hat:

Magnetic fields are spread over the whole universe. Galaxies as well as galaxy groups and cluster exhibit magnetic fields. In Fig. 1 the magnetic field lines of an edge-on spiral galaxy is shown. In Fig. 2 the same is shown for a face-on spiral galaxy. One of the main fields of interest of modern astrophysics is to find the origin and mechanisms of the observed cosmic magnetic fields on galactic and cosmological scales.

Fig. 1, Left: Edge-on spiral galaxy NGC 891 (total and polarized intensity), observed with the Effelsberg telescope at 8 GHz (3.6 cm wavelength) Optical background image: CFHT/Coelum
© M. Krause (MPIfR  Bonn)


Fig. 2, Right: Spiral galaxy M51 (total and polarized intensity), combined from data observed with the  interferometric radio telescope Very Large Array (VLA, USA)  and the Effelsberg 100m single-dish radio telescope (Germany) at 5 GHz (6 cm wavelength), Optical background image: Hubble Space Telescope (Hubble Heritage Team)

© A. Fletcher (MPIfR  Bonn)




The Galaxy survey “Continuum HAlos in Nearby Galaxies – an Evla Survey (CHANG-ES)“ was observed at the Expanded - Very Large Array (E-VLA Radiotelescope), New Mexico, USA (Fig. 3). It contains a galaxy sample of significant size over a variety of angular spatial scales, which will help to address fundamental questions regarding radio halos and magnetic fields in spiral galaxies. The PI of this Project is our VIP of the Ruhr-University Bochum Judith Irwin.

Fig. 3: Expanded - Very Large Array (E-VLA Radiotelescope), New Mexico, USA.

©Yelena Stein

The CHANG-ES sample of 35 galaxies are all edge-on spiral galaxies with a certain luminosity and size. In Fig. 4 you see all the galaxies.

The galaxies were observed at the two low frequencies, 1.5 GHz (20 cm wavelength) and 6 GHz (6 cm wavelength) in the radio regime to get a low contribution of thermal emission and to carry out a technique called “Faraday rotation analyses” in galaxy disks and halos. CHANG-ES can also exploit the wide bandwidths that are provided by the EVLA.  These wide bandwidths permit enormous improvements in continuum sensitivity. In addition, the wide bands provide a wealth of spectral information that will be unique to this survey. Moreover, CHANG-ES is the first survey of edge-on galaxies for which all polarization products will be obtained, providing important information on halo magnetic fields (Irwin et al. 2012).



Fig. 4 CHANG-ES logo.



Dr. Alexei Moiseev vom Special Astronomical Observatory der Russian Academy of Sciences wird vom 1.9.-30.10.2013 zu Gast am AIRUB bei PD Dr. Dominik Bomans seins. Die beiden Forscher arbeiten zusammen an Fabry-Perot Beobachtungen des ionisierten Gases in stark sternbildenden Zwerggalaxien.

Dr. Alexei Moiseev



Dr. Evgenii Vasiliev vom Dept. of Space Physics, Univ. Rostov am Don ist vom 1.-12. Juli 2013 zu Gast bei PD Dr. Dominik Bomans und wird am 11.7. um 15:30 Uhr in NA 7/32 einen Vortrag halten über "Metal ions in the ISM/IGM: equilibrium or time-dependent?".
Interessierte sind herzlich willkommen!