Yusuke Tsukamoto (RIKEN)

Title: Formation and early evolution of circumstellar disks and dust growth in their early evolution

Abstract: Circumstellar disks are the formation site of the planets and the physical property of disks eventually determines the architecture of the planetary system. In this talk, I will talk about the recent progress of the formation and evolution of the circumstellar disk. My talk will be divided into two part. In the first part, I will talk about the formation process of the circumstellar disk, particulary focusing on the influence of non-ideal magnetohydrodynamical effects (Ohmic diffusion, Hall effect, and ambipolar diffusion) on the disk formation. We find that disk size is significantly affected by whether the rotation vector and the magnetic field of the core are parallel or anti-parallel. In the former case, only a very small disk (\lt 1 {AU}) is formed. On the other hand, in the latter case, a massive and large (\gt 20 {AU}) disk is formed in the early phase of protostar formation. Since the parallel and anti-parallel properties do not readily change during the disk evolution, we suggest that disk size distribution of the Class 0 YSOs becomes bimodal. In the second part, I will discuss the dust growth in the gravitationally unstable disk in the Class 0/I phase and its influence on the dust thermal emissions that is often used to estimate the disk mass. We also discuss the possibility of the planetesimal formation in the Class 0/I YSOs. We find that the dust disk quickly settles into the steady state (within 10^5 years) and the dust thermal emission decreases by a factor of 1/3 to 1/5. This indicates that the mass of gravitationally unstable disk in the Class 0/I YSOs is underestimated by a factor of 1/3 to 1/5 when it is calculated from the dust thermal emission assuming an ISM dust-to-gas mass ratio and micron-sized dust opacity. We also find that planetesimal formation at ~ 20 AU is possible in gravitationally unstable disks.

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Last-modified: 2016-12-08 (木) 20:16:18 (292d)