Ambipolar Diffusion and Far-Infrared Polarization from the Galactic Circumnuclear Disk

Abstract

We describe an implicit prediction of the accretion disk models constructed by Wardle and Konigl (1990) for the circumnuclear disk (CND) of gas and dust near the Galactic center: supersonic ambipolar diffusion, an essential dynamical ingredient of the Wardle-Konigl disks, will cause the alignment of dust grains due to a process described by Roberge, Hanany, & Messinger (1995). We calculate synthetic maps of the polarized thermal emission which would be caused by ambipolar alignment in the preferred Wardle-Konigl model. Our maps are in reasonable agreement with 100 micron polarimetry of the CND if we assume that the grains have shapes similar to those of grains in nearby molecular clouds and that the CND contains a disordered magnetic field in energy equipartition with its ordered field.