Integrated intensity map of the C¹⁷O (1–0) line. The error on the integrated intensity is 0.02 K km s⁻¹. The black contours represent increasing 10% steps of the peak of the Herschel N(H₂) map, presented by Spezzano et al. (2016); the white dash-dotted contour shows the 70% level of the HCO (2_2,1 –1_1,1) column density map, derived as explained in Sect. 4.1; and the red dash-dotted contour shows the 14σ level (σ = 7 mK km s⁻¹) of the integrated intensity of the c-C₃H₂ (3_2,2 –3_1,3) line (Spezzano et al. 2016). The beams are shown in the bottom right corner, in yellow for Herschel/SPIRE and in white for the 30 m telescope. The black cross marks the dust continuum peak and the red triangle marks the methanol peak.