Plots of the rest velocity v_LSR versus the FWHM, derived from the Gaussian fits of the lines (Table 5). All the detected species and the relevant isotopologues of Table 5 are plotted, except those in which the lines have obviously non-Gaussian profiles (see text). In particular, the labels HCN* and OCS* mean that the main isotopologues of these species are not included, because of their non-Gaussian profiles. The one-σ error bars include fit and spectral resolution uncertainties. The vertical lines at v_LSR = 2.7 and 3.9 km s^-1 correspond to the velocity of the components B and A, respectively (see Sect. 6). The horizontal line at 5 km s^-1 corresponds approximatively to the average of the line FWHM range.