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We present a detailed study of the surface brightness profiles of densefilaments in IC 5146 using recent Herschel observations done with SPIRE. Wedescribe the profile through an equilibrium solution of a self-gravitatingisothermal cylinder pressure confined by its surrounding medium. In this firstanalysis we applied a simple modified black body function for the emissivity,neglecting any radiative transfer effects. Overall we found a good agreement ofthe observed surface brightness profiles with the model. The filaments indicatestrong self-gravity with mass line densities M/l\gtrsim 0.5 (M/l)_max where(M/l)_max is the maximum possible mass line density. In accordance with themodel expectations we found a systematic decrease of the FWHM, a steepening ofthe density profile, and for filaments heated by the interstellar radiationfield a decrease of the luminosity to mass ratio for higher central columndensity and mass line density. We illustrate and discuss the possibility ofestimating the distance, external pressure, and dust opacity. For a clouddistance D\sim500 pc and a gas temperature of T_cyl=10 K the model implies anexternal pressure p_ext/k\sim 2x10^4 K cm^-3 and an effective dust emissioncoefficient at 250 microns given by delta x kappa_0^em \sim 0.0588 cm^2 g^-1where delta is the dust-to-gas ratio. Given the largest estimate of thedistance to the cloud complex, 1 kpc, the model yields an upper limit delta xkappa_0^em \sim 0.12 cm^2 g^-1.

Estimating distance, pressure, and dust opacity using submillimeter observations of self-gravitating filaments