Diagnostic diagram employing the H₂O 179 μm/557 GHz vs. the H₂O 179 μm/CO(3–2) intensity ratios. Theoretical LVG predictions are plotted for the same parameters as in Fig. 8. The plot assumes a fixed N(CO) column density of 5 × 10¹⁵ cm^-2 (see text for details). Data points refer to intensities measured in a beam of 38′′, equal to the beam of the 557 GHz observations.