High-Resolution Millimeter-Wave Mapping of Linearly Polarized Dust Emission: Magnetic Field Structure in Orion

We present 1.3 and 3.3 mm polarization maps of Orion-KL obtained with the BIMA array at approximately 4'' resolution. Thermal emission from magnetically aligned dust grains produces the polarization. Along the Orion "ridge" the polarization position angle varies smoothly from about 10° to 40°, in agreement with previous lower resolution maps. In a small region south of the Orion "hot core," however, the position angle changes by 90°. This abrupt change in polarization direction is not necessarily the signpost of a twisted magnetic field. Rather, in this localized region, processes other than the usual Davis-Greenstein mechanism might align the dust grains with their long axes parallel with the field, orthogonal to their normal orientation.