T_rot of optically thin H₂O emission (top), optically thick H₂O emission (N = 10¹⁷ cm^-2; middle) and optically thin CO emission (bottom) determined from RADEX simulations. T_rot is calculated from the same transitions as in Sect. 2, i.e., excluding the ground-state transitions. The gray area indicates the observed values of T_rot. The points indicate the different physical conditions examined; model 1 (red) has (T, n) = (150 K, 10⁶ cm^-3) for the EHV components and (100 K, 10⁶ cm^-3) for the broad component. Model 2 (blue) has (T, n) = (500 K, 10⁵ cm^-3) for the EHV components, respectively. Model 3 (green) has (T, n) = (500 K, 10⁶ cm^-3) for all components.