Diagnostic diagram to explore the parameter (T_kin, n_H2, N_ortho−H2O, Θ) space that fits the observed data of the R4-LV component. The different panels are for three different values of the emission size (Θ =  5′′, 15′′ and 35′′) and three different temperatures (T =  150, 300 and 650 K). Three line ratios are reported in each panel: 557 GHz/1097 GHz (green), 1670 GHz/1097 GHz (blue) and 1113 GHz/1097 GHz (red); and the integrated intensity of the 1097  GHz line (cyan). An error of 10% is assumed for each line intensity. The thick boxes in this diagram and in all following diagrams mark the range of parameters for which all line ratios and line intensity intersect, corresponding to the physical conditions that are consistent with the observed data.