MAQ Magazine n. 13 / July 2019
Until today, however, a magnetic field had never been observed in the filaments that connect the clusters between them. As immense, the filaments of this web are in fact extremely rarefied and difficult to observe: "In this context, the pair of clusters Abell 0399 and Abell 0401 is truly exceptional," explains Federica Govoni, team leader of the National Institute of Astophysics-INAF. “For some time our group had discovered that both clusters have a radio halo. More recently, the Planck satellite has shown that the two systems are connected by a thin filament of matter. We investigated whether the magnetic field could extend beyond the center of the clusters, permeating the filament of matter that connects them. With great satisfaction the image obtained with the Lofar radio telescope (see next page sheet) confirmed our intuition, showing what can be defined as a sort of ‘aurora’ on cosmic scales ”.
The cosmic dawn
The emission of these radio waves is due to the synchrotron mechanism that originates when highly energetic electrons move inside a magnetic field. This mechanism of emission in action was observed in individual galaxies and even in galaxy clusters, but never before had a radio emission been observed connecting two of these systems. It is essential to understand the nature of this radio source because the electrons, during their radiative life time, manage to cover a much smaller space than the extension of the entire source. There must therefore be some mechanism responsible for their acceleration that operates along the entire strand ”. https://science.sciencemag.org/content/364/6444/981