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We characterize in detail the two ∼0.3 pc long filamentary structures found within the subsonic region of Barnard 5. We use combined Robert C. Byrd Green Bank Telescope and Very Large Array observations of the molecular lines NH3(1,1) and (2,2) at a resolution of 1800 au, as well as James Clerk Maxwell Telescope continuum observations at 850 and 450 μm at a resolution of 4400 and 3000 au, respectively. We find that both filaments are highly supercritical with a mean mass per unit length, M/L, of ∼80 M⊙ pc−1 after background subtraction, with local increases reaching values of ∼150 M⊙ pc−1. This would require a magnetic field strength of ∼500 μG to be stable against radial collapse. We extract equidistant cuts perpendicular to the spine of the filament and fit a modified Plummer profile as well as a Gaussian to each of the cuts. The filament widths (deconvolved FWHM) range between 6500 and 7000 au (∼0.03 pc) along the filaments. This equals ∼twice the radius of the flat inner region. We find an anticorrelation between the central density and this flattening radius, suggestive of contraction. Further, we also find a strong correlation between the power-law exponent at large radii and the flattening radius. We note that the measurements of these three parameters fall in a plane and derive their empirical relation. Our high-resolution observations provide direct constraints on the distribution of the dense gas within supercritical filaments showing pre- and protostellar activity. [ABSTRACT FROM AUTHOR]