Comparing Theory with Observation Using Chemical Probes of Turbulent Molecular Clouds

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AST 0307793GloverOur understanding of the interstellar clouds of molecular gas where stars form depends primarily on observations of spectral lines from trace molecules such as CO, water, and ammonia. Recent models of these molecular clouds have suggested that they are dynamical objects with lifetimes under 10 million years, and that cores within the clouds usually represent dynamically collapsing objects. However, the models yield physical variables such as density, temperature, and velocity, whichare difficult to compare directly to observed maps of line intensity. This project removes one difficulty standing in the way of that comparison by directly following the formation and evolution of molecular species in three-dimensional numerical simulations of magnetohydrodynamical turbulence, including the effects of self-gravity. Approximations will also be made to model the effects of UV radiation on the chemistry. Direct comparisons to the observations will be made by comparing measurements of chemical abundances, and by modeling line transfer through the turbulent gas with an iterative method. The simulations will be used to study a number of problems; for instance, whether current observations of molecular clouds can be used to constrain the nature of the turbulence, and whether the chemical composition of simulated cores is compatible with the observed composition of real cores.The models computed in this project will be made freely available to observers in a form suitable for simulating observations from a wide variety of different instruments, as part of the digital collection of the American Museum of Natural History. This research will also be incorporated into ongoing presentations of research to the media, in-service teachers, and the general public, as well as classes at Columbia University. This research will be done in an international collaboration withcolleagues in the United Kingdom.***