Numerical Simulations of Non-equilibrium Plasmas and Their Spectra - Applications to Active

AST-0307720 Ferland Much of our understanding of the chemical evolution of the cosmos comes from the analysis of emission or absorption lines produced in interstellar gas. This project is a simultaneous attack on several broad fronts extending from nearby HII regions to luminous quasars with the common theme of developing the tools needed to chart their chemical evolution. Much of this work centers on the development and application of the large-scale plasma simulation code Cloudy. This is a multi-pronged effort that combines observational astrophysics, numerical simulations, and atomic and molecular physics. These steps are strongly interwoven and progress from the Orion Nebula, to the giant extragalactic H II region 30 Doradus, and eventually to the intervening systems seen by their absorption lines in spectra of distant quasars. Starting with a complete model of the neutral hydrogen molecule, with a fully self-consistent spectral simulation, the project will then extend to helium-like species, with an important first application to the primordial helium abundance. With other extensions, the result should be a fully self-consistent description of how gas flows from its fully molecular state, eventually into regions where ions are formed by photo-ionization, resulting in an almost parameter-free description of the entire environment. The models will be tested against very deep optical spectroscopy of the Orion Nebula and of 30 Doradus, the nearest giant extragalactic HII region. The spectral simulation code at the heart of this project is used by other researchers in work that produces over a hundred papers a year. Code development, with strong involvement by students, including as parts of their doctoral theses, therefore has a very wide impact on the community. Results from this project will also be used by the researcher to assist with a scheme under development which will bring in-service teachers from central Kentucky to his University campus for research briefings and teaching strategy discussions.