LOFAR reveals inner workings of galaxies in its most detailed images ever

BY DR LEAH MORABITO (DURHAM UNIVERSITY)

After almost a decade of work, an international team of astronomers revealed the most detailed lowfrequency radio images yet of galaxies beyond our own, revealing their inner workings in unprecedented detail.

Much of the work was done by early career researchers. Clockwise from centre top: Etienne Bonnassieux, Roland Timmerman, Christian Groeneveld, Pranav Kukreti, Frits Sweijen, Shruti Badole; centre: Naím Ramirez-Olívencia

The images were created from data collected by the international LOFAR, a network of 110,000+ dipole antennas spread across nine European countries, with the majority located in the Netherlands. Much of the work was carried out by early career researchers who will be future key users of the SKA telescopes.

The new images reveal the inner-workings of nearby and distant galaxies at a resolution 20 times sharper than typical LOFAR images. This was made possible by the unique way the team, led by Dr Leah Morabito of Durham University in the UK, used the array. In standard operation, only the signals from antennas located in the Netherlands are combined, creating a “virtual” telescope with a collecting ‘lens’ with a diameter of 120km, corresponding to the distance between the two furthest stations. By using the signals from all of the European antennas, the team has increased the diameter of the “lens” to almost 2,000km. This required the development of special techniques.

The new radio images push the boundaries of what we know about galaxies and supermassive black holes. A special issue ofthescientificjournalAstronomy&Astrophysics is dedicated to 11 research papers describing how astronomers made theseimagesandthescientificresults. “These high resolution images allow us to zoom in to see what’s really going on when supermassive black holes launch radio jets, which wasn’t possible before at low frequencies,” said Dr Neal Jackson of The University of Manchester, cochair of the LOFAR high resolution imaging working group [alongside the author of this piece]. Even before LOFAR started operations in 2012, the European team of astronomers began working to address the colossal challenge of combining the signals from its widely distributed antennas. The result, a publicly available data-processing pipeline, (described in Morabito et al. 2021), will allow astronomers from around the world to make high-resolution LOFAR images with relative ease. Early career researchers from a range of European universities and research institutes, like ASTRON and INAF, have not only produced incredible science results using these data processing techniques, but contributedsignificantlytothedevelopmentofthepipeline. This work made use of computing resources in the UK, Italy, as well as the Netherlands.

New highresolution observations taken with LOFAR reveal that the jet in Hercules A grows stronger and weaker every few hundred thousand years. CREDIT: R. Timmerman; LOFAR & Hubble Space Telescope