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We present high resolution (~ 30 au) ALMA Band 6 dust polarizationobservations of VLA 1623. The VLA 1623 data resolve compact ~ 40 au inner disksaround the two protobinary sources, VLA 1623-A and VLA 1623-B, and also anextended ~ 180 au ring of dust around VLA 1623-A. This dust ring was previouslyidentified as a large disk in lower-resolution observations. We detect highlystructured dust polarization toward the inner disks and the extended ring withtypical polarization fractions ~ 1.7% and ~ 2.4%, respectively. The twocomponents also show distinct polarization morphologies. The inner disks haveuniform polarization angles aligned with their minor axes. This morphology isconsistent with expectations from dust scattering. By contrast, the extendeddust ring has an azimuthal polarization morphology not previously seen inlower-resolution observations. We find that our observations are well fit by astatic, oblate spheroid model with a flux-frozen, poloidal magnetic field. Wepropose that the polarization traces magnetic grain alignment likely from fluxfreezing on large scales and magnetic diffusion on small scales. Alternatively,the azimuthal polarization may be attributed to grain alignment by theanisotropic radiation field. If the grains are radiatively aligned, then ourobservations indicate that large (~ 100 um) dust grains grow quickly at largeangular extents. Finally, we identify significant proper motion of VLA 1623using our observations and those in the literature. This result indicates thatthe proper motion of nearby systems must be corrected for when combining ALMAdata from different epochs.

Dust Polarization Toward Embedded Protostars in Ophiuchus with ALMA. I. VLA 1623