PdBI+30 m CO(2−1) example spectra toward NGC 3627N (left) and NGC 3627S (right). The offsets of the positions are marked (see also Fig. 2). The green lines present the Gaussian fits to the data. The corresponding FWHM and peak positions are reported in Tables A.1 and A.2. The blue and red lines at the bottom of each panel indicate mean values of the velocities for the bar 1 scenario and the spiral described in Sect. 4. The corresponding full velocity ranges are shown in Figs. 5 and 6.