Absolute magnitude difference between the galaxies in the pair, ΔM_B (z) = |M_B,2(z) − M_B,1(z) |, as a function of redshift (thick green line). The letter in each panel refers to the companion galaxy in Fig. 4. The dashed lines mark the major merger limit, ΔM_B = 1.5. The red solid lines mark the ΔM_B computed with the absolute magnitudes estimated at the best photometric redshifts.