Description
Water ice is thought to be the most abundant volatile in a low-temperature region of protoplanetary disks. A promising tool to study water ice in disks is to observe its 3-µm feature, which is attributed to O-H vibration of water molecules in ice. The outer disk of HD 142527 is known to exhibit the 3 µm feature in disk reflected light. Honda et al. (2009) showed that dust particles should contain a significant amount of water ice to explain the observed ice feature. However, in the previous modelling, isotropic scattering of icy particles was assumed for simplicity and it is unclear how this assumption affects the ice abundance estimate. In this study, we perform 3D Monte Carlo radiative transfer simulations for the outer disk of HD 142527 and study the 3-µm ice feature in the disk reflected light spectra. As a result, we find that the isotropic scattering assumption leads to an overestimation of ice abundance for µm-sized grains, and therefore, the observed ice feature can be explained with much lower ice abundance than that inferred in the previous study. In addition, our results suggest that icy particles might be as large as 3 µm, indicating efficient vertical mixing in the disk. In the talk, we also discuss future prospects of water ice observations in disks with JWST.
