Dust settling and growth in protoplanetary disks and its implication for formation of extrasolar planets

点击翻译按钮获取中文摘要

Planetary systems are formed in protoplanetary disks that are by-products of star formation. The disks consist of 98-99 wt.% of H-He gas and residual dust grains. The dust coagulates into planetesimals and the planetesimals accrete into terrestria planets and cores of jovian planets.In this study, we investigated details of processes from dust to planetesimals. Collisions between dust grains do not necessarily result in coalescence. The conditions for coalescence of disruption were derived by numerical simulations (Wada et al. 2007). Self-gravitational instability of dust to clumps (planetesimals) was also studied by N-body simulations (Michikoshi et al. 2007). On the other hands, assuming complete sticking of dust collisions, we simulated evolution of dust size distributions as functions of radius and height of disks to calculate dust radiation from the disks and compare the results with observational data (Tanaka et al. 2005). We found that dust radiation decays on timescales of million years by growth of dust, wchich means that the decay does not necessarily imply depletion of disk gas.We also discussed implication for radio observation. With the theoretical model, we found that "AKARI" space telescope can detect dust components of disks down to Moon mass and fixed the survey project based on it. We also developed pipelines for star/planet formation study with IDL. Furthermore, we found that high-precision images by ALMA can detect difference in dust growth between inner and outer disks.