Millimeter Interferometric Polarization Imaging of the Young Stellar Object NGC 1333/IRAS 4A

Abstract

We present a 3.4 mm polarization image of the dust emission associated with the young stellar object NGC 1333/IRAS 4A made with the Owens Valley Millimeter Array with 5'' resolution. The integrated linear polarization of the dust continuum is 4% of the total intensity. The polarization is produced by magnetically aligned dust grains and arises from very dense gas (n > 108 cm-3), which indicates that the dust alignment process remains viable in the dense protostellar envelope. The magnetic field directions inferred from our observations are aligned with features seen in the high-velocity outflow emanating from IRAS 4A. The magnetic field directions are not aligned with the field on much larger scales as measured by optical and infrared selective extinction, which suggests significant field structure in the cloud core. The peak of the polarized emission is offset from the total intensity peak, which perhaps indicates considerable unresolved structure in the magnetic field.