Panel A: mass per unit length integrated over the radial column density profiles, , against median central column density, , for the 599 filaments of the selected sample. The solid straight line shows the one-parameter best-fit linear relation , where is the centralgas surface density. Panel B: plot of against for the same sample of filaments. The one-parameter best-fit linear relation is . Panel C: mass per unit length estimated as M_fil∕l_fil (where M_fil is calculated summing the column density over the pixels within the area between the filament crest and R_out, after subtraction of , see text of Sect. 3.4) against for the 1310 filaments of the “total” sample. The solid straight line shows the one-parameter best-fit linear relation .