Far-ultraviolet observations of the Rho Ophiuchi cloud complex

We refined a simulation model of dust scattering for the ρ Ophiuchi cloud complex, which was previously studied by Lee et al., by allowing multiple scatterings through clouds of varying distances and thicknesses. Whereas the optical parameters obtained in the present model are similar to the previous estimations, with 0.35 for the albedo and 0.6 for the g-factor, the present model gives a more realistic result for the clouds’ location at ∼110–130 pc with a thickness of ∼30–40 pc, in the diffuse background that is situated beyond ∼160 pc. We have also performed photodissociation simulations for the region of enhanced H2 fluorescence emission seen around the dark clouds facing the OB associations, and determined the column density of molecular hydrogen to be 1017.0 cm−2, smaller than the value given by Lee et al. by three orders of magnitude. This is due to the much higher intensity of the interstellar radiation field, which was verified by direct calculations based on a star catalogue.