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

We describe an implicit prediction of the accretion disk models constructedby Wardle and Konigl (1990) for the circumnuclear disk (CND) of gas and dustnear the Galactic center: supersonic ambipolar diffusion, an essentialdynamical ingredient of the Wardle-Konigl disks, will cause the alignment ofdust grains due to a process described by Roberge, Hanany, & Messinger (1995).We calculate synthetic maps of the polarized thermal emission which would becaused by ambipolar alignment in the preferred Wardle-Konigl model. Our mapsare in reasonable agreement with 100 micron polarimetry of the CND if we assumethat the grains have shapes similar to those of grains in nearby molecularclouds and that the CND contains a disordered magnetic field in energyequipartition with its ordered field.Comment: 14 pages (LaTeX+2 eps figs); accepted by ApJ Letters 11/19/9