Galaxy clusters are easier to see with radio-X-ray combination

Through the clever use of two types of telescopes, a team of researchers has created stunning images of galaxy clusters. Not only does this produce beautiful images, but it also provides more information about the enormous amounts of energy being released in clusters around supermassive black holes. The astronomers, led by Ph.D. student Roland Timmerman (University of Leiden, The Netherlands), will shortly publish their method in the journal Astronomy & Astrophysics.

Astronomers have long known that supermassive black holes produce giant jets at the centers of galaxies. These jets shoot away from the black hole, heating the gas in the wider area. When the jets collide with gas, they form huge lobes tens of thousands of light-years across. It can take hundreds of millions of years for these lobes to fade. Therefore, the lobes, at least theoretically, give astronomers a lot of information about what happened in a cluster.

The problem, however, is that the information is difficult to extract from the lobes. An international team of astronomers has now put an end to this. They combined measurements from the radio telescope LOFAR, whose core is in the Netherlands, with those from the X-ray satellite Chandra.

Whole greater than sum

“This combination gives a much better idea of ​​what’s going on,” explains researcher Roland Timmerman (Leiden University, the Netherlands).

“It’s a cliche, but the whole really is greater than the sum of the parts here. Chandra and LOFAR individually can give a pretty reasonable estimate of the amount of energy the black hole is pumping into the cluster environment, but together they are even stronger. Previously, this combination was not possible because radiographs of sufficient quality to match Chandra’s X-rays were not available. Since LOFAR antenna stations are now located all over Europe, the resolution is high enough.”

Astronomers now have radio images that are comparable in sharpness to visible-light images from the Hubble telescope. To demonstrate their technique, they photographed the Perseus cluster. This is a group of more than a thousand galaxies located about 240 million light-years toward the northern constellation Perseus.

Meanwhile, astronomers are creating composite images of other galaxy clusters. With the underlying data, they hope to understand more about the interactions between galaxies and their environment in the early Universe.