Top panels: Hi-GAL-250 μm map of G351 (left panel). The white solid line indicates the skeleton of the filament obtained from the Hi-GAL data. The map is divided in different regions for the estimate of the filament width along the source. Middle panel: full width at half maximum inarcsec in different regions of the filament. The cross-spine average radial profile of the observed intensity in the Hi-GAL-250 μm data (black thick line, right panel) is given for three regions (a, b, and c; these are also shown in the other two panels) along G351.The solid red line is the Gaussian fit; the thin black line shows the resolution of the data. The error bars show the dispersion of the measurements in the relative region. Bottom panels: as for the top panels but for the SABOCA data.