Top panel: N-PDFs for the atomic hydrogen for different p. The PDF is measured over the entire filament indicated with a red polygon in Fig. 14, assuming a constant spin temperature of T_HISA = 40 K. Bottom panel: N-PDFs for the atomic hydrogen for different spin temperature and different polynomial functions fit to get T_off. The dashed vertical lines in each panel indicate 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 densities for the N-PDF of “Pol 2, p = 0.9, 40 K”, i.e., the black histogram in both panels. Other N-PDFs are shifted to the correct absolute column density for comparison.