Molecular transition analysis for N₂H⁺ (J = 1–0) (top), NH₃ (1,1) (middle) and ¹³CO (J = 1–0) (bottom). First column shows the integrated intensity between −42.5 and −33 km s⁻¹. The second column shows the radial velocity and the third column shows the velocity dispersion. The over-plotted contour corresponds to an H₂ column density of 0.312 × 10²³ cm⁻² (see Sect. 4.1). Each dataset has been masked according to this contour and is used to estimate the properties of G316.75 in Table 3. The molecular transition used has been labeled in the bottom right of of the first column. The open black circle in the last column shows the FWHM beam size of the observations. The crosses in the first row show the positions of the clumps and the black arrow in b show the location and the direction along which the N₂ H⁺ spectra presented in Fig. 9 were taken.