Upper panel: continuum emission map at 3 mm (from Fontani et al. 2017) in colour scale with H¹³CN (1−0) emission overlaid in black contours. Contours start at the level of 4σ, corresponding to 0.70 mJy beam⁻¹ (1σ = 0.18 mJy beam⁻¹) and are in intervals of 6σ, corresponding to 1.17 mJy beam⁻¹. Lower panel: same as the upper panel but the black contours show the HC¹⁵N (1−0) average emission. Contours start at the level of 4σ, corresponding to 0.84 mJy beam⁻¹ (1σ = 0.21 mJy beam⁻¹) and are in levels of 4σ, corresponding to 0.84 mJy beam⁻¹. Continuum sources identified by Neri et al. (in prep.) are marked by white triangles. The wedge on the right indicates the range of flux density (Jy beam⁻¹). The ellipse in the bottom-left corner of each panel represents the NOEMA synthesised beam of the 3 mm continuum emission.