Top: Radio and X-ray surface brightness comparison of LOFAR and uGMRT images at a resolution of 50′′ × 50′′ with an X-ray XMM image of A773 within the regions marked by boxes in Fig. D.1. Bottom: Same but for A1351 at a 33′′ × 33′′ resolution. The red line indicates the best fit, and the dashed blue line is the 2σ contour threshold. The Pearson correlation coefficient is denoted by r_p, with the corresponding p-values in brackets. σ indicates the scatter around the best-fit relation.