| Abstract: | This study reports the first detection of a radio megahalo in the massive merging galaxy cluster PLCKG287.0+32.9, using deep, wide-band uGMRT observations at 300-850 MHz. The cluster exhibits a complex array of diffuse radio emissions, including a large radio halo, two relics, and filamentary structures, which provide insights into the dynamics of merger-driven particle re-acceleration. These sensitive observations reveal the radio halo extending to ∼ 3 Mpc, doubling the previously known extent and reaching the cluster’s R500 radius along an intergalactic filament. The radial surface brightness profile shows the halo is two component halo - inner component is typical giant radio halo and outer one is megahalo, both possibly energised by merger induced turbulence. These findings represent the first megahalo detection at frequencies above 144 MHz, paving the way for further high-frequency studies to enhance our understanding of the origins and evolution of megahalos in merging galaxy clusters. Along with this, the detected relics exhibit asymmetric positions relative to the cluster centre, with the northern relic showing an unusual "inverted" structure, spectral steepening on both sides, and signs of re-energised plasma from a nearby radio galaxy. This relic’s atypical orientation and spectral features likely result from an in-falling substructure bending the outgoing shock inward, as suggested by optical studies identifying substructures within the cluster. |
