The MeerKAT Massive Distant Clusters Survey: a search for diffuse radio emission in 30 massive SZ-selected clusters at <i>z</i> &amp;gt; 1

Abstract

ABSTRACT 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 $z \gt 1$, 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 ($P_{1.4\, \mathrm{GHz}}$) and cluster mass ($M_{\rm 500c}$) in this high-redshift sample. It is well established that radio haloes 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 haloes in eight clusters (27 per cent), while the remaining 21 (70 per cent) show no emission; one additional cluster (3 per cent) 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 $\lesssim 10{{\ \rm per\ cent}}$ occurrence generally predicted by theoretical models at $z \gtrsim 1$. The detected radio haloes scatter around the best-fitting $P_{1.4\, \mathrm{GHz}}$–$M_{\rm 500c}^{\rm {Unc}}$ 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-haloes 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 $P_{1.4\, \mathrm{GHz}}$–$M_{\rm 500}$ relation across cosmic time.