2D histograms showing the distribution of the linewidths of spectra (i.e., the FWHM of the Gaussian fits to their main peaks) within filaments over their distance from the core they are connected to in H¹³CO⁺(1–0). The yellow line and dots show the median value of each column. Left: all cores. Middle: evolved cores (A, B). Right: younger cores (C–F). The spike in the mean value for cores C-F at ~1 pc is likely caused by unresolved multiple components and low statistical sampling.