Magnetic fields in star-forming molecular clouds. V. Submillimeter polarization of the Barnard 1 dark cloud

We present 850 mum polarimetry from the James Clerk Maxwell Telescope toward several dense cores within the dark cloud Barnard 1 in Perseus. Significant polarized emission is detected from across the mapped area and is not confined to the locations of bright cores. This indicates the presence of aligned grains and hence a component of the magnetic field in the plane of the sky. Polarization vectors detected away from bright cores are strongly aligned at a position angle of similar to90degrees (east of north), while vectors associated with bright cores show alignments of varying orientations. There is no direct correlation between the polarization angles measured in earlier optical polarimetry toward Perseus and the polarized submillimeter thermal emission. Depolarization toward high intensities is exhibited but toward the brightest core reaches a threshold beyond which no further decrease in polarization percentage is measured. The polarized emission data from the interior envelope are compared with previously published OH Zeeman data to estimate the total field strength and orientation under the assumption of a uniform and nonuniform field component in the region. These results are rough estimates only as a result of the single independent detection of Zeeman splitting toward Barnard 1. The uniform field component is thus calculated to be B-0 = 31 muG [+/-(0.52 (N) over cap -0.01 (E) over cap)- 0.86 (z) over cap] in the case in which we have assumed the ratio of the dispersion of the line-of-sight field to the field strength to be 0.2.