NH₃ velocity dispersion, , as a function of position along the blue filament (blue dots) and the red filament (red dots). Each data point is the median value of the velocity dispersion for the points across the filament for a given position along the filament, and the error bars indicate the median of the uncertainty of the values of the velocity dispersion for the same points. The dashed lines indicate the average sound speed, c_s, of the filaments, 0.26 km s⁻¹ (blue filament) and 0.29 km s⁻¹ (red filament), and the dotted lines indicate average thermal width (see text), 0.10 km s⁻¹ (blue filament) and 0.11 km s⁻¹ (red filament). The slices used are the same as in Fig. 11.