Astronomers Spot Two Galaxy Clusters About to Merge Connected by a Magnetic Field

galaxy cluster

A unique merger between galaxy clusters has unveiled a strange event. Astronomers spot a vast, low-frequency radio “bridge” between the two, crossing a 6.5-million-light-year distance – proof of a magnetic field connecting them in the initial phase of the merging process. 

The event is the second to be observed, but it already provides some key clues as to how these bridges evolve. These galaxy clusters are about 3 billion light-years away, in a community dubbed Abell 1758. All four clusters are in this impeding connection – two giant cluster pairs merging. Here is what you need to know.

A Radio Bridge and Two Galaxy Clusters: a Cosmic Story

In 2019, X-ray data showed that the tightly bound pair in the north segment dubbed Abell 1758N, have traveled together and separated. Then, the cluster cores passed each other about 300 to 400 million years ago. They’ll find, however, their way back to each other eventually. 

As for the pair of galaxy clusters in the south, named Abell 1758S, is getting closer for the first time, highlighting a unique moment. 

Recently, a team of astrophysicists conducted by Andrea Botteon from the Leiden Observatory in the Netherlands has put the low-frequency radio telescope, LOFAR, in the direction of Abell 1758. They found radio emission stretching between A1785N and A1785S, at 144 megahertz and confirmed the presence of a massive giant bridge of radio emission. The finding is now proof of a vast magnetic field connecting the two galaxy clusters, the second event to date.

Furthermore, if this magnetic field acts as a particle accelerator, electrons should be accelerated along with it to relativistic speeds, generating synchrotron radiation seen as a low-frequency radio glow. Botteon and his team offer two supporting arguments to the recent event.

Firstly, a lighter mass batch of merging clusters, with only one of them possessing a radio halo, showed no proof of a radio bridge in LOFAR investigations. And secondly, the team examined observations of Abell 1758 utilizing the Chandra X-ray Observatory. They discovered that the X-ray emission is closely correlated with the radio emission at 144 megahertz. 

It seems that there are various types of acceleration at play. What completes the bridge is that special something such as shock waves and turbulence. 

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