Radiactive signatures of dust and lines: From protostellar disks to active galactic nuclei

This proposal requests continuation of support for an ongoing, long-term program in which practical radiative transfer methods are developed and refined to match the progress made by new observations. The program has had a transformative impact on studies of astronomical masers and dust infrared emission from active galactic nuclei (AGN). With the requested funds we propose to expand and eithance two radiative transfer techniques developed with recent support-a new exact method for line emission from multi-level systems and the handling of radiation from clumpy media. These enhancements will be used in the following projects: (1) Improved models of the dust emission from AGN that will be matched against forthcoming high-resolution observations; (2) new calculations of line emission from AGN removing faulty assumptions that have been employed in all modeling attempts to date; (3) a realistic calculation of radiation pressure on dust to examine a recent proposal that this force may provide hydrostatic support for the AGN torus; (4) a broad study of the thermal and maser line emission from accretion disks to establish clear disk signatures in objects ranging from young stellar objects to AGN. A major ingredient of the proposed research is the close collaboration with the observing teams conducting the pertinent observations. Broad Impact: This theory program is strongly anchored in observations and has always ap- pealed to a large number of observers. Modeling codes developed in the conduct of this research have been placed in the public domain and used in many studies unrelated to this research pro- gram. The P1 is involved in a broad range of international collaborations that include numerous female colleagues. In addition to advancing knowledge and understanding within different fields of studies, a major accomplishment of this program has been its continuing educational impact. Every graduate student trained under this program who has received his/her degree over the past twenty years, including those holding positions at teaching colleges, continues to maintain an ac- tive collaboration with it.