Close-up view of the Hα emission line profiles for the galaxies satisfying one of the two precoalescence criteria defined in Sect. 4.1. In each panel, as a consequence of the sky-subtraction procedure applied to the 2D spectra, the lines appear twice in different slit positions, in the first with a positive flux (in yellow) and in the second with a negative flux (in black). For each cutout, we show with two white arrows the slit position (s) and the dispersion direction (λ), which are slightly rotated due to the curved Magellan spectra. In order to clarify the classification criteria adopted in this work for finding precoalescence SBs, we highlight: (1) with continuous lines the different tilting angles of Hα line profiles (first three SBs); (2) with dotted ellipses the spatially separated Hα lines coming from different merger components (last four SBs).