Recent research achievements

A new map of the sky with hundreds of thousands of galaxies

© RUB, Marquard

The group of Prof. Dettmar from the Astronomical Insitute contribute to the special issue of the journal "Astronomy & Astrophysics".

A team of astronomers from the Ruhr-Universität Bochum (RUB) has studied one of the discovered galaxies in detail and found a characteristic radiation distribution that suggests processes in the formation of galaxies and our Milky Way. 

The Lofar Telescope 

Lofar is a vast European network of radio telescopes linked together by a high-speed fibre-optic network, whose measurement signals are combined into a single signal. Powerful supercomputers convert 100,000 individual antennas into a virtual reception dish with a diameter of 1,900 kilometers. Lofar operates in the frequency ranges between about 10 to 80 megahertz and 110 to 240 megahertz, which have so far been largely unexplored. It is controlled by the Astron research facility in the Netherlands and is considered the world's leading telescope of its kind. There are six measuring stations in Germany which are operated by various scientific institutions.

Supernovae influence the evolution of galaxies

Dr. Arpad Miskolczi of the RUB Chair of Astronomy is one of the first authors of the collection of research results, all based on the analysis of a first phase of the multi-year project. In collaboration with international colleagues, he has investigated one of the many newly discovered galaxies in more detail. The object with the catalogue name NGC 3556 shows a characteristically different radiation distribution in the radio range than in visible light. "From this we conclude that the accumulation of numerous huge stellar explosions, so-called supernovae, releases so much energy that the gas between the stars, interspersed with magnetic fields and particles of cosmic rays, leaves the galaxy,"; explains Prof. Dr. Ralf-Jürgen Dettmar. These processes have influenced the evolution of Milky Way systems over billions of years. By comparing different such objects, the researchers hope to gain information about the origin of our own Milky Way.

Black holes, magnetic fields, galaxy clusters

With the help of Lofar, scientists have been able to create a new sky map. Many of the galaxies depicted were previously unknown because they are extremely far away and their radio signals have to travel billions of light years to reach Earth.

When scientists observe the sky with a radio telescope, they mainly see radiation from the vicinity of black holes, which are millions of times heavier than the sun. With Lofar, the researchers want to find out what influence the black holes have on the galaxies in which they are located and where they come from. Thanks to Lofar's sensitivity, the teams have already been able to show that black holes are present in all giant galaxies and that they are constantly growing. 

The radio radiation received by Lofar can also be used to measure cosmic magnetic fields. The researchers have also been able to detect magnetic structures between galaxies, thus proving theoretical assumptions for the first time. 

The fusion of two clusters of galaxies produces radio emissions - so-called radio halos - with a size of millions of light years. With Lofar they can be tracked down. The researchers learn a lot from this about the gas at the edge of the gigantic clusters of galaxies.

Gigantic amounts of data

The creation of low frequency radio sky maps requires both considerable telescope and computational time and requires analysis of the data by large teams. "Lofar produces gigantic amounts of data - we have to process the equivalent of ten million DVDs. This places the highest demands on software and hardware and is only possible through an international and interdisciplinary team,"; says Prof. Dr. Dominik Schwarz of Bielefeld University and representative of Germany to the Lofar steering committee. 

"In Germany, we worked together with Forschungszentrum Jülich to efficiently convert the huge amounts of data into high-quality images. These images are now public and will allow astronomers to study the evolution of galaxies in unprecedented detail,"; adds Prof. Dr. Ralf-Jürgen Dettmar. 

The Forschungszentrum Jülich accommodates around 15 petabytes of Lofar data. "This is almost half of all Lofar data, one of the largest astronomical data collections in the world. The processing of these gigantic data sets represents a great challenge. What would have taken centuries on conventional computers could have been reduced to one year by using innovative algorithms and extremely powerful computers,"; says Prof. Dr. Dr. Thomas Lippert, Director of the Jülich Supercomputing Centre. Jülich is one of the three data centres of the Lofar project. In addition, the Jülich Supercomputing Centre manages the data network traffic between the German Lofar stations and the central Lofar computer in Groningen.

15 million radio sources expected

The 26 papers now published in a special issue of Astronomy & Astrophysics are based on only about two percent of the observations planned with Lofar. The scientists now want to map the entire northern celestial sphere. After all, they expect to find around 15 million radio sources.

The original press releases can be found here.