Left panel: LOFAR (upper) and uGMRT (lower) surface brightness maps of SDSSTG8102 shown in colour. The contours start with 3σ_rms × [1, 2, 4,...], with σ_rms = 110 μJy beam⁻¹ (at 144 MHz) and 30.5 μJy beam⁻¹ (at 400 MHz). The green circle marks the BGG of the group. The white line in the lower image shows the location of the change in surface brightness. Middle panel: Radio surface brightness map for SDSSTG16393 (at 8″ resolution) shown at both frequencies and with a similar contour level as the upper panel. The rms values are σ_144 MHz = 92 μJy beam⁻¹ (upper) and σ_400 MHz = 32 μJy beam⁻¹ (lower). Right panel: Same but for SDSSTG28674 (at 7″ resolution) and with similar contour levels as the left panel. The rms values are σ_144 MHz = 85.1 μJy beam⁻¹ (upper) and σ_400 MHz = 28.7 μJy beam⁻¹ (lower).