a) Modelled lines fluxes (105-600) for the considered density ranges (colored points) compared to observations (black diamonds). Uncertainties of observations are not plotted because they are smaller than the marker. b) χ² comparing observed line integrated intensities of 105-600 and modelled values for the considered envelope and disk densities. c) Temperature at the ionisation front, overlaid are the χ² contours. d) Temperature at the disk surface. In panels b, c, d, points are the positions where the models are calculated and the colors and contours result from interpolating the model results over these points.