Molecular line radiative transfer in protoplanetary disks
Résumé
We analyze the line radiative transfer in protoplanetary disks using several approximate methods and a well-tested Accelerated Monte Carlo code. Uniform molecular abundances as well as those from a chemical model are adopted. Radiative transfer in low and high rotational lines of CO, C18O, HCO+, DCO+, HCN, CS, and H2CO is simulated. We find that the simple Local Thermodynamical Equilibrium (LTE) and Full Escape Probability (FEP) approaches are not accurate in some cases, while Large Velocity Gradient (LVG) and Vertical Escape Probability (VEP) methods can be safely applied. A new concept of interacting cells that allows to accelerate a Monte Carlo code by an order of magnitude is introduced.