N-PDFs for the two subregions within the filament marked with dashed polygons in Fig. 14. Top and bottom panels: N-PDF of atomic and molecular hydrogen derived with HISA and ¹³CO measurements, respectively. The lighter lines show the log-normal (top and bottom panels) and power-law (bottom panel) fits. The black dashed lines in each panel mark the column density threshold, and the solid vertical lines indicate the mean column densities. The bottom x-axes in both panels are the relative column density for the N-PDF of the western subregion, i.e., the red histogram in both panels. Other N-PDFs are shifted to the correct absolute column density for comparison. The thick black line in the molecular component panel shows the power-law fit with an index − α to the column density distribution of the western region.