THREE-DIMENSIONAL RADIATION TRANSFER IN YOUNG STELLAR OBJECTS

Abstract

We have updated our publicly available dust radiative transfer code\n(HOCHUNK3D) to include new emission processes and various 3-D geometries\nappropriate for forming stars. The 3-D geometries include warps and spirals in\ndisks, accretion hotspots on the central star, fractal clumping density\nenhancements, and misaligned inner disks. Additional axisymmetric (2-D)\nfeatures include gaps in disks and envelopes, "puffed-up inner rims" in disks,\nmultiple bipolar cavity walls, and iteration of disk vertical structure\nassuming hydrostatic equilibrium. We include the option for simple power-law\nenvelope geometry, which combined with fractal clumping, and bipolar cavities,\ncan be used to model evolved stars as well as protostars. We include\nnon-thermal emission from PAHs and very small grains, and external illumination\nfrom the interstellar radiation field. The grid structure was modified to allow\nmultiple dust species in each cell; based on this, a simple prescription is\nimplemented to model dust stratification.\n We describe these features in detail, and show example calculations of each.\nSome of the more interesting results include the following: 1) Outflow cavities\nmay be more clumpy than infalling envelopes. 2) PAH emission in high-mass stars\nmay be a better indicator of evolutionary stage than the broadband SED slope;\nand related to this, 3) externally illuminated clumps and high-mass stars in\noptically thin clouds can masquerade as YSOs. 4) Our hydrostatic equilibrium\nmodels suggest that dust settling is likely ubiquitous in T Tauri disks, in\nagreement with previous observations.\n