Early investigations suggested that the galaxy cluster PSZ2G181.06+48.47, shown above, was an ordinary low-mass collection of galaxies. Later, radio observations revealed something remarkable: a pair of parenthesis-shaped radio sources located several million light-years from the center of the cluster. In a recent research article, Kamlesh Rajpurohit (Center for Astrophysics ∣ Harvard & Smithsonian) and collaborators used the Giant Metrewave Radio Telescope and the Karl J. Jansky Very Large Array to investigate PSZ2G181.06+48.47’s double radio sources, which are visible in red in the composite radio, optical, and X-ray image shown above. The team classified these features as radio relics, which are diffuse, extended, highly polarized radio sources that may be generated by shocks propagating through the intracluster medium. Radio relics are fairly rare, and PSZ2G181.06+48.47’s relics are unusual for several reasons: 1) there are two of them, and only about 30 double radio relics are known; 2) the galaxy cluster isn’t very massive, and relics are rare in low-mass clusters; and 3) the relics are separated from one another by about 11 million light-years, which is the largest separation known. To learn more about this pair of radio relics, including their likely cause, be sure to check out the full research article linked below.
Citation
“PSZ2 G181.06+48.47. II. Radio Analysis of a Low-Mass Cluster with Exceptionally Distant Radio Relics,” Kamlesh Rajpurohit et al 2025 ApJ 984 25. doi:10.3847/1538-4357/adbbb9