Radio ridge between two galaxy clusters bridges intergalactic space

Rodiano Bonacci
Giugno 8, 2019

Govoni is lead author of a study published in Science that provides the first observation of a magnetic field within the filaments connecting two galaxy clusters-what the researchers call a "radio ridge". This map shows the all the known galaxy clusters and filaments within 500 million light-years of Earth (Abell 0399 and 0401 are not among them).

In particular, she and her colleagues were intrigued because they had already determined that both of the galaxy clusters were among the few dozen with magnetic fields that scientists have spotted.

On the big roadmap of the universe, bustling clusters of galaxies are connected by long highways of plasma weaving around the wilderness of empty space. Electrons moving very, very fast inside of a magnetic field produce synchrotron radiation, which scientists can see as radio emissions. "Up to now, however, a magnetic field has never been observed in the filaments connecting clusters".

So, the next question was whether this filament between the two colliding galaxy clusters also had a magnetic field, and the best way to find out was to look for radio emissions between the two clusters.

The researchers studied two galaxy clusters dubbed Abell 0399 and Abell 0401 using the Low-Frequency Array, or LOFAR, based in the Netherlands.

"The presence of this filament stimulated our curiosity and prompted us to investigate whether the magnetic field could extend beyond the center of the clusters, permeating the filament of matter that connects them".

Even though they're separated by a distance of millions of light-years, Abell 0399 and Abell 0401 are creating a great deal of gravitational disturbance in the space around them as they draw inexorably closer together. This, they say, means some unknown mechanism that re-accelerates the electrons is happening. In the simulations, shock waves generated by the merger re-accelerated high-speed electrons, resulting in an emission consistent with the LoFar observations.

The team says their findings suggest current theories about particle acceleration in intergalactic space need to be revisited.

Leah Morabito, from the Department of Physics at the University of Oxford, U.K., who was not involved in the study, said the discovery was exciting as it provides an insight into how the cosmic web really works. That instrument's to-do list includes studying magnetic fields within the cosmic web itself, just like the one Govoni and her colleagues found here.

Julie Hlavacek-Larrondo, from the Université de Montréal, Canada, who was also not involved in the research, said: "The detection of the radio bridge is a direct testimony to the dynamic nature of galaxy clusters and the dynamic nature of the Universe on the largest scales".

Using the low-frequency radio telescope LoFar, which consists of 25,000 antennas across 51 locations, the team homed in on the filament, detecting a "ridge" of low-frequency radio emission extending between them. Nor do we know how prevalent these pre-existing relativistic electrons are in the cosmic web.

Altre relazioniGrafFiotech

Discuti questo articolo

Segui i nostri GIORNALE