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 B IMA array at approximately 4 " resolution. Thermal emission from magnetical ly aligned dust grains produces the polarization. Along the Orion "ridge" t he polarization position angle varies smoothly from about 10 degrees to 40 degrees. in agreement with previous lower resolution maps. In a small regio n south of the Orion "hot core," however, the position angle changes by 90 degrees. This abrupt change in polarization direction is not necessarily th e signpost of a twisted magnetic field. Rather, in this localized region, p rocesses other than the usual Davis-Greenstein mechanism might align the du st grains with their long axes parallel with the field, orthogonal to their normal orientation.