The MeerKAT Massive Distant Clusters Survey: a search for diffuse radio emission in 30 massive SZ-selected clusters at z > 1

We present the results of a search for diffuse radio emission in a uniformly selected sample of 30 of the most massive Sunyaev–Zel’dovich selected galaxy clusters at z > 1, providing the first statistical constraints on the evolution of cluster-scale diffuse emission beyond this redshift. We also analyse the scaling relations between radio power (P1.4 GHz) and cluster mass (M500c) in this high-redshift sample. It is well established that radio halos are primarily found in the most massive clusters, where turbulent energy from major mergers can re-accelerate relativistic electrons and amplify magnetic fields on megaparsec scales. Deep MeerKAT 1.28 GHz observations reveal diffuse radio halos in eight clusters (27%), while the remaining 21 (70%) show no emission; one additional cluster (3%) was excluded from the radio analysis due to poor data quality. The halo detection rate in this high-redshift sample is lower than at intermediate redshift, but remains higher than the ≲ 10% occurrence generally predicted by theoretical models at z ≳ 1. The detected radio halos scatter around the best-fitting P1.4 GHz–M500cUnc relation derived for the MMDCS sample, whereas non-detections populate the lower envelope of the radio power-mass plane, similar to trends seen at lower redshift. No cluster-scale radio relics or mini-halos are identified. Our findings highlight MeerKAT’s ability to probe non-thermal processes in the most distant clusters and the need for deeper, lower-frequency surveys to uncover faint diffuse emission and test the persistence of the P1.4 GHz–M500 relation across cosmic time.