High circular polarization of near infrared light induced by micron-size
  dust grains
  We explore the induction of circular polarization (CP) of near-infrared light
in star-forming regions using three-dimensional radiative transfer
calculations. The simulations trace the change of Stokes parameters at each
scattering/absorption process in a dusty gas slab composed of aligned grains.
We find that the CP degree enlarges significantly according as the size of dust
grains increases and exceeds $\sim 20$ percent for micron-size grains.
Therefore, if micron-size grains are dominant in a dusty gas slab, the high CP
observed around luminous young stellar objects can be accounted for. The
distributions of CP show the asymmetric quadrupole patters regardless of the
grain sizes. Also, we find that the CP degree depends on the relative position
of a dusty gas slab. If a dusty gas slab is located behind a star-forming
region, the CP reaches $\sim 60$ percent in the case of $1.0~{\rm \mu m}$ dust
grains. Hence, we suggest that the observed variety of CP maps can be explained
by different size distributions of dust grains and the configuration of aligned
grains.
