Surface brightness maps for the head-on mergers described in Sect. 3.2. As in the previous maps, time is in Gyr, with t = 0 at the start of the simulation and the box size is 1.6 Mpc. In each panel is indicated the collision model whose initial merging parameters are given in Table 5. Each row of panels refers to simulations with the same value of the mass ratio q, while each column is for simulations having the same value of V. This is reported in km s⁻¹. The maps are extracted at output times when the distance d_DM between the mass centroids of the two clusters is approximately d_DM ≃ 700 kpc. As in Fig. 1, the crosses indicate the projected spatial locations of the mass (green) and X-ray surface brightness (red) centroids.