Oral Presentation
Radial variations of grain size and turbulence in protoplanetary disks revealed by ALMA polarization
Presenter: Satoshi Ohashi (RIKEN)
Recent ALMA polarization observations have been showing that self-scattering is one of the important mechanisms for polarization in protoplanetary disks.
By using radiative transfer modeling, we found that the grain size and dust scale height are the key parameters for reproducing the radial and azimuthal distributions of the observed polarization signature.
Based on detailed modeling, we found the following radial variations in the grain size and dust scale height in the HD 163296 disk.
The maximum grain size was 140 microns in the gaps and significantly larger or smaller in the rings. The dust scale height is less than one-third the gas scale height inside the 70 au ring, and two-thirds the gas scale height outside the 70 au ring. The transition of the dust scale height (and turbulence strength) at the boundary of the 70 au ring indicates the existence of a dead zone.
We also show our current study of ALMA polarization observation toward the IRS 48 disk, which has a prominent lopsided structure.
We discuss the inconsistency of grain size measurements by spectral index and millimeter-polarization observations.
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