Icy grains play an important role on planet formation and related matters. Therefore, to reveal ice dust distribution within a protoplanetary disk is an critical work for understanding planet formation. Recently, we deployed thermal infrared (TIR) polarization capabilities on the existing IRCS instrument at the Subaru Telescope. This is a unique enhancement because no other 8-meter class telescope has a high-resolution polarization imaging mode in TIR wavelength. There is a H2O ice absorption band in the 3um. A comparison of the surface brightness at K-band (2.20um), H2O narrowband (3.05um), and L’-band (3.77um) allows us to probe the presence of H2O ice grains in protoplanetary disks. In order to aim to detect icy absorption features in the disk surface, we propose to observe 2 Herbig Ae stars and 2 T Tauri stars with disks using the TIR polarization imaging mode. Since all disks have a low inclination from face-on (i = 10-35 degrees), it would be possible to do the water ice mapping in the disks along the radial direction. Our proposed observation will provide not only the information for the presence of water ice (location of snow line within disks) but also the dust properties, which will be one of the important progresses to understand the role of water for the planet formation.
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