Thursday 24 August at 2:30pm

ABSTRACT: "Molecular clouds, aside from their role as stellar nurseries, are locales of inherently interesting physics wherein self-gravity, pressures and kinetic and magnetic energies compete to create massive, long-lived complexes. Myers & Goodman (1988) provided convincing arguments that equipartition exists between gravitational, kinetic and magnetic energies, but the actual structure of the magnetic fields in star-forming regions and the mechanics by which they would thus provide support remains difficult to measure. The only method of measuring the plane-of-sky field orientation is by observing the polarized emission or absorption created by aligned, rotating dust grains. Because dust grains both extinct as well as polarize light, observations in the optical and near-IR can only reach Av of 3 and 40 mag respectively. In recent years, submm polarimetry has enabled the probing of field structure in significantly more extincted regions, such as the nearby Orion A molecular cloud. We will present our observations of a small 6' portion of Orion A's Integral-Shaped Filament, itself over 30' in length as well as a twisted filament in Orion B. Based on these 2D polarimetric maps, we argue that the field in these regions cannot be uniform and that our maps show strong evidence that the magnetic field is either affecting the structures being formed by the gas, or is being dragged along with it. The depolarization effect, recognized to exist towards most bright intensity sources, exists along the length of the Orion A filament we have mapped and could be due to an underlying helical field structure."