After almost a decade of work, an international team of astronomers has published the most detailed images yet seen of galaxies beyond our own, revealing their inner workings in unprecedented detail. The images were created from data collected by the Low Frequency Array (LOFAR), a network of more than 70,000 small antennae spread across nine European counties, with its core in Exloo, the Netherlands. The results come from the team’s years of work, led by Dr Leah Morabito at Durham University.

The 70,000+ LOFAR antennae spread across Europe are combined to create a ‘virtual’ telescope with a collecting ‘lens' with a diameter of almost 2000 km, which provides a twenty-fold increase in resolution in comparison with observing with Dutch stations only. The six LOFAR stations run by GLOW (Jülich, Effelsberg, Tautenburg, Unterweilenbach, Potsdam, and Norderstedt) provided essential observational coverage because of their geographical location within the International LOFAR telescope, which is indispensable to make images at such a high resolution.

The team’s work forms the basis of nine scientific studies that reveal new information on the inner structure of radio jets in a variety of different galaxies as well as a publication describing the publicly-available data-processing pipeline, developed with assistance from GLOW members, in detail. This will allow astronomers from around the world to use LOFAR to make high-resolution images with relative ease.

Since LOFAR must stitch together the data gathered by more than 70,000 antennae, processing is a huge computational task. To produce a single image, more than 13 terabits of raw data per second – the equivalent of more than a three hundred DVDs – must be digitised, transported to a central processor and then combined. This is a challenge that can only be mastered with supercomputers. The Forschungszentrum Jülich hosts one of the LOFAR Long-Term Archives that stores about half of all observations conducted with the LOFAR telescope.


Figure: Illustration of the gain in resolving power if using the full LOFAR-VLBI network including all European stations. The inner structure of the radio galaxy is not visible in the upper central image at 6‘‘ resolution (using the Dutch stations only). With the full LOFAR-VLBI array it is possible to achieve a resolution of about 0.3‘‘ allowing the observer to reconstruct unprecedented details of the inner structure of radio galaxies.

Revealing a hidden universe of light in HD

The new images, made possible because of the international nature of the collaboration, pushing the boundaries of what we know about galaxies and super-massive black holes. Super-massive black holes can be found lurking at the heart of many galaxies and many of these are ‘active’ black holes that devour in-falling matter and belch it back out into the cosmos as powerful jets and outflows of radiation. These jets are invisible to the naked eye, but they burn bright in radio waves and it is these that the new high-resolution images have focused upon. Dr Neal Jackson of The University of Manchester, said: “These high resolution images allow us to zoom in to see what’s really going on when super-massive black holes launch radio jets, which wasn’t possible before at frequencies near the FM radio band”.

"We are very happy that many years of hard work enable us now to efficiently process all European LOFAR stations in a way to make use of the highest possible resolution the LOFAR telescope is able to provide. This allows us to gain breathtaking images from the inner-most regions of radio galaxies", said Dr Alexander Drabent from the Thüringer Landessternwarte in Tautenburg, "With this step, LOFAR enters still unknown territory at such low frequencies".


Links: Press Release (ASTRON)