2005A&A...434..167S

Constraints on the density and thermal 3D structure of the dense molecular cloud core ρ Oph D are derived from a detailed 3D radiative transfer modeling. Two ISOCAM images at 7 and 15µm are fitted simultaneously by representing the dust distribution in the core with a series of 3D Gaussian density profiles. Size, total density and position of the Gaussians are optimized by simulated annealing to obtain a 2D column density map. The projected core density has a complex elongated pattern with two peaks. We propose a new method to calculate an approximate temperature in an externally illuminated complex 3D structure from a mean optical depth. This ``T_<τ>''-method is applied to a 1.3mm map obtained with the IRAM 30m telescope to find the approximate 3D density and temperature distribution of the core ρ Oph D. The spatial 3D distribution deviates strongly from spherical symmetry. The elongated structure is in general agreement with recent gravo-turbulent collapse calculations for molecular clouds. We discuss possible ambiguities of the background determination procedure, errors of the maps, the accuracy of the T_<τ>-method and the influence of the assumed dust particle sizes and properties.