Fig. : LOFAR image of the cluster PSZ2G091.83+26.11 at a redshift of z=0.822. The brightness of the emission is outlined by the contour lines overlayed.

From a study of nine ancient galaxy clusters with the radio telescope LOFAR, a group of European radio astronomers concluded that the built-up of magnetic fields must have been fast during the formation of the clusters. The observations were taken from the ongoing LOFAR Two-metre Sky Survey (LoTSS), which has surveyed currently about 40% of the Northern Sky. The group, led by Gabriella Di Gennaro from Leiden Observatory (Netherlands), included several members from GLOW institutes. They selected distant clusters, which emitted their radio light when the Universe was only half of its present age, and compared them with local galaxy clusters. They then found that the luminosities of the diffuse radio emission associated with the ancient clusters are similar to those of the local ones. As the magnetic field strength in the diffuse regions is correlated with the luminosities, the observations infer that the magnetic field strengths (which are of the order of a few microgauss) must have been created rapidly in the young universe and did not evolve further until today. These findings were recently published in Nature Astronomy.  "The study shows the potential of LOFAR's sensitive low-frequency observations to uncover the role of magnetic fields in the formation of the largest structures in the Universe", comments co-author and GLOW chair Matthias Hoeft (Thüringer Landessternwarte, Germany).

Find more information at Leiden University: Astronomers see gigantic collisions of galaxy clusters in young universe