We present a detailed study of the surface brightness profiles of dense filaments in IC 5146 using recent Herschel observations done with SPIRE .
We describe the profile through an equilibrium solution of a self-gravitating isothermal cylinder pressure confined by its surrounding medium .
In this first analysis we applied a simple modified black body function for the emissivity , neglecting any radiative transfer effects .
Overall we found a good agreement of the observed surface brightness profiles with the model .
The filaments indicate strong self-gravity with mass line densities M / l > \sim 0.5 ( M / l ) _ { max } where ( M / l ) _ { max } is the maximum possible mass line density .
In accordance with the model expectations we found a systematic decrease of the FWHM , a steepening of the density profile , and for filaments heated by the interstellar radiation field a decrease of the luminosity to mass ratio for higher central column density and mass line density .
We illustrate and discuss the possibility of estimating the distance , external pressure , and dust opacity .
For a cloud distance D \sim 500 ~ { } { pc } and a gas temperature of T _ { cyl } = 10 ~ { } { K } the model implies an external pressure p _ { ext } / k \sim 2 \times 10 ^ { 4 } ~ { } { K~ { } cm ^ { -3 } } and an effective dust emission coefficient at 250 ~ { } \mu { m } given by \delta \kappa _ { 0 } ^ { em } \sim 0.0588 ~ { } { cm ^ { 2 } ~ { } g ^ { -1 } } where \delta is the dust-to-gas ratio .
Given the largest estimate of the distance to the cloud complex , 1 kpc , the model yields an upper limit \delta \kappa _ { 0 } ^ { em } \sim 0.12 ~ { } { cm ^ { 2 } g ^ { -1 } } .