Submillimeter polarization observation of the protoplanetary disk around
  HD 142527
  We present the polarization observations toward the circumstellar disk around
HD 142527 by using Atacama Large Millimeter/submillimeter Array (ALMA) at the
frequency of 343 GHz. The beam size is $0.51 " \times 0.44 "$, which
corresponds to the spatial resolution of $\sim$ 71 $\times$ 62 AU. The
polarized intensity displays a ring-like structure with a peak located on the
east side with a polarization fraction of $P= 3.26 \pm 0.02$ %, which is
different from the peak of the continuum emission from the northeast region.
The polarized intensity is significantly weaker at the peak of the continuum
where $P= 0.220 \pm 0.010$ %. The polarization vectors are in the radial
direction in the main ring of the polarized intensity, while there are two
regions outside at the northwest and northeast areas where the vectors are in
the azimuthal direction. If the polarization vectors represent the magnetic
field morphology, the polarization vectors indicate the toroidal magnetic field
configuration on the main ring and the poloidal fields outside. On the other
hand, the flip of the polarization vectors is predicted by the self-scattering
of thermal dust emission due to the change of the direction of thermal
radiation flux. Therefore, we conclude that self-scattering of thermal dust
emission plays a major role in producing polarization at millimeter wavelengths
in this protoplanetary disk. Also, this puts a constraint on the maximum grain
size to be approximately 150 ${\rm \mu m}$ if we assume compact spherical dust
grains.
