Evolution of the main haloes in the pair region in the three main projection axes (z, y, and x, from left to right). The maps show the projected gas density within a (20 h⁻¹ cMpc)³ comoving volume centred on the final (at z = 0.07) pair centre of mass for different redshifts between z = 0.47 and z = 0.07 (from top to bottom). We mark GC1 and GC2 (red cross and yellow asterisk, respectively), the two northern groups A and B (green square and red diamond), and the additional main group-size haloes in the region (white triangles) and their progenitors. For each halo, circles approximate their R₂₀₀ extent, except for group B at z ≲ 0.16, when it is identified as a substructure gravitationally bound to GC1. For GC1 and GC2, the dot-dashed circles at z = 0.07 correspond to 3 × R₂₀₀.