Gaussian line fits using the CASSIS software. The upper panel shows the spectra of the HDO transition at 225.9 GHz, while the lower panel is for the transition at 203.4 GHz. The left plots are for the M position with the fit of the component at 6 km s⁻¹ (blue), while the right plots are for the N position with the fit of the component at 9 km s⁻¹ (red). The dotted lines indicate the central velocity of the respective Gaussian. The green line shows the corresponding double-Gaussian profiles (see Table A.2).