Characteristics of Collapse of Rotating Isothermal Clouds : Astrophysics and Relatively

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概要

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• In order to solve the long.standing ``centrifugal bounce or runaway'' problem and also the problem of subsequent dynamical evolution, the collapse of rotating isothermal clouds has been investigated by axisymmetric two・dimensional simulations and also by one-dimensional analysis as well as simulations in a thin disk approximation. For the initial condition, we have considered flattened configurations besides a uniform sphere. The results show that the collapse of the inner region follows a series of similar disk-like configurations nearly independent of initial and boundary conditions: The angular velocity and the column density of the disk are both proportional to (a_c^2+ω^^~^2)^<-1>, and the equatorial density to (a_c^2+ω^^~^2)^<-1> where a_c is the core radius decreasing with time and ω^^~ is the distance from the rotation axis. This similarity law arises from a competition between gravity and pressure in the core, contrary to the previous belief that centrifugal force would play a more significant role than pressure. The above form of column density shows that an axisymmetric disk cloud does undergo runaway collapse as long as it is isothermal, as was found in the simulations of Norman et al. The inner region is not very flattened (its axial ratio or flatness being about 6); hence, it is unlikely that the inner region will be subject to ring formation during the isothermal collapse. However, as for the outer envelope, whether it becomes gravitationally unstable to ring formation depends on its initial condition, i.e., the magnitudes of initial flatness and also density fluctuation. It is also shown that the above mentioned central runaway occurs only when the gas is isothermal. However, the runaway is actually stopped because the core becomes opaque and the gas is no more isothermal. It is found that the departure from isothermality gives rise to a bounce of the core and that, if the cloud is very flattened, it becomes unstable to ring formation, but otherwise it oscillates around an equilibrium state.

• 理論物理学刊行会の論文
• 1984-12-25

著者

• Miyama S

  National Astronomical Observatory

• Miyama Shoken

  Department Of Physics Kyoto Unvi

• Miyama Shoken

  Department Of Physics Kyoto Univeristy

• Narita Shinji

  Department of Electronic Engineering, Doshisha University

• Narita Shinji

  Science And Engineering Research Institute Doshisha University

• Hayashi C

  Kyoto University

• Narita S

  Science And Engineering Research Institute Doshisha University

• NARITA Shinji

  Department of Electonics, Doshisha University

関連論文

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• The Structure and Evolution of Thin Viscous Disks-1-Non-steady Accretion and Excretion
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• Chapter 8 Efficiency of Angular Momentum Transfer by Shear Instability : Part II Formation Processes of Protostars : Origin of the Solar System
• Chapter 7 Stability of the Primordial Solar Nebula : Part II Formation Processes of Protostars : Origin of the Solar System
• Rapid Contraction of Protostars to the Stage of Quasi-Hydrostatic Equilibrium. III : Stars of 0.05, 1.0 and 20Mxodoi with Energy Flow by Radiation and Convection
• Collapse and Flare-up of Protostars
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• Chapter 4 The Equilibrium and the Stability of Rotating Isothermal Clouds : Part II Formation Processes of Protostars : Origin of the Solar System
• Fragmentation of Isothermal Sheet-Like Clouds. II : Full Nonlinear Numerical Simulations
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