Left panel: mean radial column density profile of the L1157 filament (gray points) measured perpendicular to the crest of filament shown in Fig. 1. The gray error bars mark the ± 1σ dispersion of the distribution of radial profiles along the spine of the filament. The solid black curve shows the best-fit Plummer model fitted on the mean radial profile. The black dashed curve marks the best-fit Gaussian function to the inner radius of the profile. The thin solid black curve represents the Gaussian profile of the beam. Right upper panel: deconvolved Gaussian FWHM of the L1157 filament as a function of position along the crest of the filament (starting from southern core toward the central protostar). Right lower panel: the central column density along the crest of the filament obtained from the best-fit Plummer model is plotted as the dashed black line. Background-subtracted mass-per-unit length calculated from the Gaussian fit (dashed gray line). The dashed gray horizontal line indicates the critical mass-per-unit length or line mass of an isothermal filament in equilibrium as 2c/G ~ 15 M_⊙ pc⁻¹ at 10 K.