We investigate structure of self-gravitating disks, their fragmentation and evolution of the fragments (the clumps) using both analytic approach and three-dimensional radiation hydrodynamics simulations starting from molecular cores. The simulations
show that non-local radiative transfer determines disk temperature. We find the disk structure is well described by an analytical model of quasi-steady self-gravitating disk with radial radiative transfer. Because the radiative process is not local and radiation from the interstellar medium cannot be ignored, the local radiative cooling would not be balanced with the viscous heating in a massive disk around a low mass star. In our simulations, there are cases in which the disk does not fragment even though it satisfies the fragmentation criterion based on disk cooling time ($Q sim 1$ and $Omega t_{rm cool}sim 1$). This indicates that at least the criterion is not sufficient condition for fragmentation. We determine the parameter range for the host cloud core in which disk fragmentation occurs. In addition, we show that the temperature evolution of the center of the clump is close to that of typical first cores and the minimum initial mass of clumps to be about a few Jupiter mass.
We investigate the accretion of angular momentum onto a protoplanet system using three-dimensional hydrodynamical simulations. We consider a local region around a protoplanet in a protoplanetary disk with sufficient spatial resolution. We describe th
e structure of the gas flow onto and around the protoplanet in detail. We find that the gas flows onto the protoplanet system in the vertical direction crossing the shock front near the Hill radius of the protoplanet, which is qualitatively different from the picture established by two-dimensional simulations. The specific angular momentum of the gas accreted by the protoplanet system increases with the protoplanet mass. At Jovian orbit, when the protoplanet mass M_p is M_p < 1 M_J, where M_J is Jovian mass, the specific angular momentum increases as j propto M_p. On the other hand, it increases as j propto M_p^2/3 when the protoplanet mass is M_p > 1 M_J. The stronger dependence of the specific angular momentum on the protoplanet mass for M_p < 1 M_J is due to thermal pressure of the gas. The estimated total angular momentum of a system of a gas giant planet and a circumplanetary disk is two-orders of magnitude larger than those of the present gas giant planets in the solar system. A large fraction of the total angular momentum contributes to the formation of the circumplanetary disk. We also discuss the satellite formation from the circumplanetary disk.
