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J. F. Fiege (National Research Council of Canada)
Fiege & Pudritz (2000) developed models of self-gravitating filamentary molecular clouds threaded by a helical magnetic field. Other equilibrium models of filaments exist, including the unmagnetized Ostriker (1964) model, and the magnetized model of Stodolkiewicz (1963).
Sub-millimetre continuum and polarization maps provide stringent contraints on theoretical models. Grains emit thermal radiation at sub-mm wavelengths, which is partially polarized orthogonal to the magnetic field direction projected on the plane of the sky. Thus, sub-mm continuum maps determine the core radius and the radial surface density structure of the filament, while polarization maps probe the geometry of the magetic field.
We demonstrate a new technique designed to simultaneously model the I, Q, and U Stokes parameters at sub-mm wavelengths. We use a niched pareto multi-objective genetic algorithm to locate the best-fitting set of models in the ``pareto-optimal surface'' or ``trade-off surface'', where none of the fits (I, Q, or U) can be improved without degrading at least one other. In principle, Zeeman data or line emission maps could be added without difficulty to further constrain the models.
Several models are shown for various filaments to illustrate the usefulness of this technique. We discuss the physical implications of the best-fitting models.
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.