Combined LOFAR-uGMRT analysis of the diffuse radio emission in the massive clusters Abell 773 and Abell 1351

Context. Radio halos are diffuse megaparsec-scale nonthermal radio sources located at the center of galaxy clusters. They trace relativistic particles and magnetic fields in the intra-cluster medium. The source of energy for their formation is believed to be the merging of galaxy clusters, which generates turbulence and reaccelerates aged electrons. Aims. We studied the diffuse radio emission, spectral properties, and the connection between thermal and nonthermal emission in the massive (M 500 ∼ 7 × 10 14 M ⊙), dynamically disturbed galaxy clusters Abell 773 and Abell 1351. Methods. We combined observations from the LOFAR Two-meter Sky Survey Data Release 2 at 144 MHz and the new upgraded Giant Meterwave Radio Telescope at 650 MHz for both clusters. Archival XMM-Newton X-ray images were utilized to supplement our analysis. Results. We confirm that both clusters host a radio halo, each of which has a largest linear size of ∼2 Mpc. We measure an integrated spectral index (₁₄₄^650) of ∼ − 1. 0 for both clusters. Via point-to-point analysis, we show that the radio halo in A773 resembles a classical radio halo that follows a sublinear relation between radio and X-ray surface brightness. Conversely, A1351 exhibits a more complex and asymmetric radio halo that is embedded with several radio sources, including the brightest cluster galaxy, a tail galaxy, and the ridge. We find a deviation from the sublinear relation in the point-to-point analysis that is due to the presence of these contaminating radio sources.