Astronomers Take Best Look Yet At The Radio Structures Within Galaxy Clusters

VLA image of radio-emitting mini-halo in the Perseus Cluster. The radio emission is in red and visible light is in white. Gendron-Marsolais et al./NRAO/AUI/NSF/NASA/SDSS.

Astronomers have looked at the radio emission of a famous galaxy cluster and discovered a wider range of complex structures than they were expecting.

The cluster in question is the Perseus cluster located 250 million light-years away and known for a gigantic gas tsunami rolling across it. The cluster also has the largest known radio emission, called a “mini-halo”, which is 1.3 million light-years across.

The halo is made of radio-emitting particles, which have puzzled scientists as they should slow down and stop their emission. However, they don’t seem to care much about what they should or shouldn’t do.

Thanks to the newly upgraded National Science Foundation’s Karl G. Jansky Very Large Array (VLA), astronomers have been able to study the Perseus mini-halo and gain new insight into the production of the radio waves in the cluster. The results are published in the Monthly Notices of the Royal Astronomical Society.

“The new VLA images provided an unprecedented view of the mini-halo by revealing a multitude of new structures within it,” co-author Julie Hlavacek-Larrondo, from the University of Montreal, said in a statement. “These structures tell us that the origin of the radio emission is not as simple as we thought.”

According to the study, the halo’s radio emission is generated by complex interactions within the clusters. Particles are accelerated by the gravitational pull of galaxies entering the cluster with their intergalactic gas, as well as by the powerful jets of supermassive black holes located at the center of many galaxies and emitted by the large elliptical galaxy located at the core of the Perseus cluster.

The combination of these two effects is believed to be sufficient enough to create the intricate structures witnessed by the VLA. The powerful radio telescope, immortalized in the movie Contact, was first built in the 1970s and has undergone a complete decade-long refurbishment, which ended in 2012. The upgrade is clearly paying off.

“The high-quality images that the upgraded VLA can produce will be key to helping us gain new insights into these mini-haloes in our quest to understand their origin,” Hlavacek-Larrondo added.

The Perseus cluster, also known as Abell 426, is one of most massive objects in the known universe. It has hundreds of times the mass of the Milky Way contained in its mini-halo region and also hosts hundreds if not thousands of galaxies. The researchers hope that studying its radio emission will help us understand the checkered history of this behemoth.

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