Interferometric Mapping of Magnetic Fields in Star‐forming Regions. III. Dust and CO Polarization in DR 21(OH)

Abstract

We present the polarization detections in DR 21(OH) from both the thermal dust emission at 1.3 mm and the CO J=2-->1 line obtained with the Berkeley-Illinois-Maryland Association array. Our results are consistent with the prediction of the Goldreich-Kylafis effect that the CO polarization is either parallel or perpendicular to the magnetic field direction. The detection of the polarized CO emission is over a more extended region than the dust polarization, while the dust polarization provides an aid in resolving the ambiguity of the CO polarization. The combined results suggest that the magnetic field direction in DR 21(OH) is parallel to the CO polarization and therefore parallel to the major axis of DR 21(OH). The strong correlation between the CO and dust polarization suggests that magnetic fields are remarkably uniform throughout the envelope and the cores. The dispersion in polarization position angles implies a magnetic field strength in the plane of the sky of about 1 mG, compared to about 0.5 mG inferred for the line-of-sight field from previous CN Zeeman observations. Our CO data also show that both MM 1 and MM 2 power high-velocity outflows with v>~25 km s-1 relative to the systemic velocity.