Collapse of Rotating Gas Clouds and Formation of Protostellar Disks: Effects of Temperature Change during Collapse

摘要: We show two-dimensional numerical simulations of the gravitational collapse rotating gas clouds. assume polytropic equation state, P = Kργ, to take account temperature change during collapse. Our have two model parameters, β and γ, which specify initial rotation velocity index, respectively. three models, 1.0, 0.5, 0.2, for each is taken be 0.8, 0.9, 0.95, 1.05, 1.1, or 1.2. These 18 models are compared with previously reported isothermal (γ 1). In a cylindrical cloud initially in equilibrium fragments periodically because growth perturbation forms cores. The core becomes dynamically collapsing gaseous disk whose central density (ρc) increases time (t) proportion ρc ∝ (t - t0)-2. This qualitatively similar distributions runaway cloud. surface disk, Σ, proportional power radial distance, Σ(r) r1-2γ, envelope. Models γ > 1 geometrically thick disks (aspect ratio rd/zd 2), while those 10). While former stable, latter unstable against fragmentation if we adopt Toomre stability criterion thin disk. also rotationally supported by accretion period t t0 1. phase starts at stage still finite. beginning lower when larger. applicable star formation primordial clouds increase due less efficient cooling.