Left: column density map of the Serpens South filament (36′′ resolution) derived from HGBS data (see Könyves et al. 2010), with the corresponding topological filament identified overlaid in blue. Right: mean radial density profile (taken from both sides of the filament) measured perpendicular to the supercritical Serpens South filament (left) shown here in log-log format. Lines and colour coding are consistent with Figs. 3 and 4. The Gaussian fit to the inner part of the profile (dotted blue curve) has a deconvolved FWHM width 0.10 ± 0.05 pc. The best Plummer-like model fit (dashed red curve) has an inner radius R_flat ~ 0.03 ± 0.01 pc and a power-law index p = 2.02 ± 0.27.