(Left-column figure) Derived FWHM_b of the Gaussian profile fitted to the cavity shock component of the H₂O lines (top-panel) as a function of bolometric luminosity. Constrained FWHM_b for the ¹²CO J = 10–9 and J = 3–2 observations (middle-panel) versus L_bol. Ratio calculated from the ¹²CO FWHM_b divided by the FWHM_b of the H₂O lines (bottom-panel) as a function of L_bol. (Right-column figure) Same as left- figure but plotted versus the envelope mass of the source, M_env. The blue plus symbols correspond to the low-mass Class 0 protostars, the black triangles the low-mass Class I, the green asterisks the intermediate-mass objects, the pink crosses the high-mass YSOs for which the ¹²CO J = 3–2 spectra are taken, and the red cross symbols the high-mass object for which ¹²CO J = 10–9 data are available (see San José-García et al. 2013). The low- and intermediate-mass objects with detected EHV components are surrounded by a box. Also the high-mass YSO with triangular water line profiles is surrounded by a box. The value of the FWHM_b of the different velocity components is calculated as explained in Sect. 2.5 and these parameters are the same for the three water transitions.