Left: Spitzer 8 μm flux density in units of MJy sr⁻¹, overlaid with IRAM 30m MAMBO 1.2 mm dust continuum contours in steps of 5 mJy beam⁻¹, from 3 to 88 mJy beam⁻¹. Crosses denote the positions of identified 1.2 mm MAMBO compact sources (white for starless and blue for proto-stellar, Peretto et al. 2014) and two 1.3 mm SMA continuum sources (in black crosses, McGuire et al. 2016). Middle: H₂ column density map in units of 10²² cm⁻², derived fromthe NH₃ integrated intensity. Overlaid contours are placed in 1 × 10²² cm⁻² steps, from 2 × 10²² cm⁻² to 12 × 10²² cm⁻². Right: extracted cores (black crosses, numbered according to Table 2) and filaments (labelled coloured lines). The extraction of these structures are discussed in Sect. 4. Extra cores at the outskirts of the north-east and south-east arms are in the more diffuse regions of the cloud where the spines did not extend through. Spine colours match those in subsequent figures.