Mass per unit length as a function of position along the blue filament (blue dots) and the red filament (red dots). The mass per unit length is obtained from the sum of NH₃ column densities across the filament, for each position along the slice. The horizontal solid lines indicate the average value for the wholefilament, 61.2 M_⊙ pc⁻¹ (blue filament) and 53.0 M_⊙ pc⁻¹ (red filament). The dashed lines indicate the critical mass per unit length for thermal and non-thermal support, (Table 2), 42.8 M_⊙ pc⁻¹ (blue filament), and 50.2 M_⊙ pc⁻¹ (red filament). The slices used are the same as in Fig. 11.