Normalized surface brightness maps of the shock front for the ℳ_i = 3 case in the fresh-injection model (first row) and re-acceleration model with a Dirac Delta (second row) and a power-law (third row) fossil populations. Each sub-panel shows four different frequencies, namely 150 MHz, 1.5 GHz, 14.25 GHz, and 18.6 GHz. The first (last) four columns correspond to ℳ_cr = 1 (ℳ_cr = 2.3), γ_cut = 10² (γ_cut = 10³), and s = 2.25 (s = 3), respectively. The time-step selected of the simulation is 120.7 Myr (see the top corner of each sub-panel).