Left panel: integrated intensity map of the strongest methanol transition observed (2_0,2 –1_0,1, A⁺). The black contours represent increasing 10% steps of the N column density map, derived by Spezzano et al. (2016) using Herschel/SPIRE data. The noise in the integrated intensity is 0.02 K km s⁻¹. The white dash-dotted line indicates the cut used for comparison with the models (see Sect. 5). Middle panel: integrated intensity map of the deuterated methanol (2_0,2 –1_0,1) transition. The black contours represent increasing 10% steps of the CH₃OH column density map, derived as explained in Sect. 4.1. The error on the integrated intensity is 0.005 K km s⁻¹. Right panel: integrated intensity map of the deuterated methanol (3_0,3–2_0,2) transition. The black contours represent increasing 10% steps of the CH₃OH column density map, derived as explained in Sect. 4.1. The error on the integrated intensity is 0.004 K km s⁻¹. In all panels the beams are shown in the bottom right corner of the figure, in yellow for Herschel/SPIRE and in white for the 30 m telescope; the black cross marks the dust continuum peak and only pixels with detection level above 3σ are included.