Radiative transfer in the clumpy environment of young stellar objects

We developed a Monte-Carlo code for the treatment of the radiative transfer in arbitrary clumpy dust configurations. Both the radiation of the (centra l) energy source(s) and the thermal emission of the dust are considered. In tensity and polarization maps of the modelled objects can be computed. As the first application of our code we studied the radiative transfer in a spherical two-phase clumpy dust shell containing a single star. The struct ure of the circumstellar dust density distribution is characterized by the filling factor of high-density clumps, the density ratio between the low an d the high density phases and the size of the smallest individual clumps. Firstly, we considered the properties of the clumpy structures of that mode l using the percolation theory. Particularly, we checked different ways to describe the optical depth. Secondly, we investigated the total stellar flu x, the mean scattering number and the absorption of the stellar radiation d epending on the filling factor, the density ratio, the optical depth, the d ust grain size and the smallest clump size. Thirdly, we compared the polari zing influence of a clumpy and an homogeneous dust shell. Fourthly, we inve stigated the influence of a clumpy density structure on the surface brightn ess distribution. First results show significant changes in the spectral energy distribution as well as in images of clumpy dust configurations in comparison to their h omogeneous counterparts.