An article published in the journal “Science Advances” reports the results of a study of the galaxy cluster Abell 2255 which for the first time detected a radio glow on a scale so large that it surrounded the entire cluster. A team of researchers used the LoFar radio telescope for 18 nights over an area four times the size of the full moon to achieve such a detailed result. According to the researchers, the origin of that emission which is at least 16 million light-years wide is linked to the energy released during the cluster formation.
About 1.5 billion light-years away from Earth, the galaxy cluster Abell 2255 is a vast ensemble that includes thousands of galaxies that could be the result of various mergers between smaller clusters. Understanding the dynamics in that environment is difficult with various processes taking place and energy emissions.
The image (Courtesy ROSAT/LOFAR/SDSS/Botteon, et al.) shows a composite view of the galaxy cluster Abell 2255. In blue, X-ray data from the ROSAT space telescope archive showing hot gas between the galaxies. The data collected by LoFar are shown in yellow and purple. The purple glow consists of radio emissions that surround the entire cluster. The yellow streaks are high-velocity particles in the cluster’s magnetic fields. The background image is from the SDDS.
The environment in the Abell 2255 cluster is chaotic and therefore beautiful for astronomers. Already in July 2020 an article published in “The Astrophysical Journal” described it thanks above all to observations conducted with the LoFar radio telescope, formed by thousands of low-cost antennas present mainly in the Netherlands but also in other European countries. The authors intended to conduct more studies and a part of that team together with other colleagues used LoFar again, focusing this time on the glow that emerged from hot plasma inside but also around Abell 2255 with other very interesting results.
The goal of this new study was to understand the origin of that plasma, which is hot but rarefied. The research focused in particular on the most energetic particles in that plasma and how they interact with the magnetic fields of galaxy clusters.
To obtain the necessary data, the researchers conducted much longer observations than usual. On average, the observations conducted with the LoFar radio telescope last about 8 hours while these new observations of the galaxy cluster Abell 2255 continued for 18 nights. The data were integrated with X-ray observations obtained from the ROSAT space telescope archive.
The result was the discovery of a glow coming from the galaxy cluster Abell 2255 with an extension never seen before since it is at least 16 million light-years. According to the researchers, that emission is generated by high-energy particles that move at speeds close to the speed of light in magnetic fields that are very weak but fill the entire cluster. They believe that this is a process that began during the formation of the cluster, with turbulence and shocks that accelerated the particles.
The LoFar radio telescope network made it possible to examine a galaxy cluster in a way never seen before. The researchers intend to continue studies of Abell 2255 and other galaxy clusters, also with instruments that will enter service in the coming years. The LoFar radio telescope network will be enhanced and SKA, the next-generation radio telescope, is under construction, instruments that will be invaluable to keep on investigating processes related to galaxy clusters, including the filaments that connect them.
