a) Mass per unit length, M_line (M_⊙ pc^-1), along the main filament derived as explained in Sect. 2.3. The light gray area indicates M_line,crit = 17.9−19.6 M_⊙ pc^-1. For illustration, the positions of the YSO (Sect. 3) and the cold dense cores studied by Juvela et al. (2010, 2011) are indicated (solid vertical line markers). Several other sharp peaks seen in the M_line graph are related to candidate dense cores (dotted vertical line markers). b) Radial column density profile perpendicular to the major axis of the filament and averaged along its length. The yellow area shows the dispersion along the filament length. The red and dashed curves show the best Gaussian and Plummer function fits (see Sect. 2.3). The inner blue curve corresponds to the 18.2″ beam resolution of the column density maps. c) POS orientations of the magnetic field as derived from starlight polarization (blue lines, Pereyra & Magalhães 2004) and polarized dust 850 μm emission observed by Planck at 9.6′ angular resolution (yellow lines of arbitrary length, Planck Collaboration Int. XXXIII 2016) overlaid on the SPIRE 250 μm map. Equatorial north-east directions are indicated by the compass (corresponding to a rotation of 55° counter-clockwise with respect to north is up). The angular and spatial scales are indicated by the horizontal line in the bottom panel: 10′ is equivalent to 0.58 pc. d) Distributions of position angles for low-density filaments/striations (green), optical polarization vectors (blue), and polarized emission vectors (rotated by + 90° to trace the POS magnetic field direction; yellow).