A MeerKAT L-band study of LOFAR-selected radio halos

Galaxy clusters are the largest gravitationally bound structures in the Universe. During cluster mergers, turbulence and shock waves can re-accelerate relativistic particles, producing diffuse radio emission. Studying their spectral properties helps us understand how particles are accelerated and how these processes relate to the dynamical state and mass of galaxy clusters. This thesis investigates diffuse radio emission in 13 galaxy clusters observed with MeerKAT in L-band. Compact radio sources were removed, and the data were reprocessed at lower resolution to better reveal extended emission. Diffuse radio emission was detected in all 13 clusters, although a detailed quantitative analysis was possible for only 11. Their radio properties were measured using exponential fits and flux estimates within the radio contours. By combining MeerKAT observations with lower-frequency data from LOFAR, integrated spectral indices and spatially resolved spectral index maps were obtained. The analysed clusters have a median spectral index of -1.13, with only one source classified as an ultra-steep spectrum radio halo. The spectral index maps reveal irregular spatial variations, with no common pattern emerging across the sample. The spectral properties were also examined in relation to cluster dynamical state and mass, using the c-w diagram and the radio power–mass relation. Overall, this work provides new insights into diffuse radio emission in galaxy clusters and contributes to our understanding of the particle re-acceleration processes that produce it.