Through the clever use of two types of telescopes, a team of researchers has produced stunning images of clusters of galaxies. This not only produces beautiful images but also provides more information about the enormous amounts of energy released around supermassive black holes in clusters. The astronomers, led by Ph.D. student Roland Timmerman (Leiden University, the Netherlands), will soon publish their method in the journal Astronomy & Astrophysics.
Astronomers have long known that supermassive black holes at galaxies' cores emit powerful jets. These jets blast away from the black hole, heating the surrounding gas. When the jets are hit with gas, they create massive lobes tens of millions of light-years across. These lobes can fade out over hundreds of millions of years. Thus, at least in principle, the lobes provide astronomers with a wealth of information about what happened in a cluster.
The difficulty is that the information in the lobes is difficult to retrieve. That has finally been laid to rest by an international team of astronomers. They merged data from the radio observatory LOFAR, the core of which is located in the Netherlands, with data from the X-ray spacecraft Chandra.
According to Roland Timmerman (Leiden University, the Netherlands), this combination offers a considerably greater understanding of what is going on. It's cliche, but the total is truly more than the sum of its parts in this case. Chandra and LOFAR can each make a good approximation about the quantity of energy delivered into the cluster environment, but combined they are considerably more powerful. Previously, this combination was not conceivable since no radio pictures of adequate quality to match Chandra's X-ray photos were available. Because LOFAR antenna sites are now spread across Europe, the resolution is adequate.
Astronomers now have radio pictures that are as crisp as visible-light photographs from the Hubble Space Telescope. They photographed the Perseus cluster to show their approach. This is a cluster of about a thousand galaxies situated around 240 million light-years away in the direction of the northern constellation Perseus.
Meanwhile, researchers are constructing composite views of other galaxy clusters. They want to learn more about the interactions between galaxies and their environs in the early universe by using the underlying data.
Journal Information: R. Timmerman et al, Measuring cavity powers of active galactic nuclei in clusters using a hybrid X-ray-radio method. A new window on feedback opened by subarcsecond LOFAR-VLBI observations, Astronomy & Astrophysics (2022). DOI: 10.1051/0004-6361/202243936Preprint: arxiv.org/abs/2207.05088