We found a new mechanism of millimeter-wave polarization of protoplanetary disks; the self-scattering. If the dust distribution has anisotropies such as ring or lopsided structure, the thermal emission is scattered by large dust grains to emit polarization at millimeter wavelengths. This will be a new probe of grain growth in protoplanetary disks. We also show an application to HL Tau.

T. Muto (Kogakuin U.), M. Momose, T. Tsukagoshi (Ibaraki U.), M. Fukagawa (Nagoya U.), H. Shibai (Osaka U.), T. Hanawa (Chiba U.), K. Murakawa Osaka-S.), Kees Dullemond, Adriana Pohl (Heidelberg)