The MeerKAT Galaxy Cluster Legacy Survey – II. Catalogue of the diffuse radio emission in MeerKAT-GCLS clusters

We present a follow-up study focused on cluster-scale diffuse radio emissions in 115 galaxy clusters in the Southern sky, using full-resolution ($7.8\, \rm arcsec$) and tapered low-resolution ($15\, \rm arcsec$) images from the MeerKAT Galaxy Cluster Legacy Survey (MGCLS). In this MGCLS follow-up paper, we update and quantitatively characterize the presence of diffuse radio emission and provide detailed catalogue information on its radio properties at 1.28 GHz. As the MGCLS sample is heterogeneous and was initially used as a test bed to reveal the scientific potential of MeerKAT, the reported numbers are subject to this special case. More than half ($\sim$54 per cent; 62/115) of the observed MGCLS clusters present diffuse cluster radio emission, with the total number of diffuse radio sources or candidates detected being 103. Including candidates, we find that radio relics are the most frequently detected diffuse sources in MGCLS at 53 per cent (55/103), followed by haloes at 32 per cent (33/103) and mini-haloes at 10 per cent (11/103), with only 3 per cent (3/103) being Phoenixes. The sizes of the diffuse radio structures and candidates range from $\sim$ 55 kpc to over 2 Mpc, with P$_{1.28\, \mathrm{GHz}}$ radio power ranging from $\sim 10^{22}$ W Hz$^{-1}$ to greater than 10$^{25}$ W Hz$^{-1}$. In-band radio spectral index estimates reveal revived radio plasma emissions that exhibit steep radio spectral indices down to $\alpha _{908}^{1656}\sim -3.5$. Mini-haloes and their respective candidates are detected mainly in low-mass (M$_{500}$ $\le$ 5$\times 10^{14}$ M$_{\odot }$) and low-power (P$_{1.4\, \mathrm{GHz}}$ $\le$ 10$^{23}$ W Hz$^{-1}$) systems. We suggest the presence of a statistically significant correlation between the 1.4 GHz radio power and the cluster mass for mini-halo (and candidate) systems.