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B.C. Matthews, C.D Wilson (McMaster University)
One of the outstanding questions in the study of star formation concerns the role of magnetic fields in the formation and evolution of clouds, cores and finally protostars. Regardless of theoretical predictions as to the amount of support magnetic fields need to provide, measurement of field patterns and strengths could end the speculation. Emission polarimetry toward highly extincted molecular clouds provides the net orientation of the plane-of-sky magnetic field in the vicinity of ongoing star formation. To compare field configurations under different conditions of star formation, areas of Orion A, Orion B, Perseus and \rho Ophiuchus have been observed with the SCUBA polarimeter at the JCMT.
The OMC-3 filament in Orion A exhibits strong alignment of the polarization vectors with the filament emission along much of its length, confirming that either the dense gas is responding to the magnetic field pattern, or vice versa. The pattern cannot be explained by a unidirectional field. The ordering and depolarization features of the polarization pattern are predicted by a recent model for filamentary clouds threaded by helical fields (Fiege & Pudritz 2000), and even an abrupt change in vector orientation at the southern boundary can be explained by this model. The second filament observed, NGC 2068 in Orion B, exhibits very different behavior. Despite ordering and depolarization, the polarization pattern varies its orientation with respect to the filament. Whether this effect can be explained by changing inclinations with respect to the plane of the sky remains to be determined. Time permitting, data obtained toward the dark clouds Barnard 1 (Perseus) and \rho Ophiuchus will also be discussed.
Funding for this research has been provided by the Natural Science and Engineering Research Council of Canada and the Ontario Graduate Scholarship Program.