标题： 旋转磁化云核中原恒星盘形成的约束条件 显示英文标题

标题： Constraints on the Formation and Evolution of Circumstellar Disks in Rotating Magnetized Cloud Cores

摘要： 我们使用磁坍缩模型来对嵌入在磁化云核中的原恒星盘的形成和角动量演化施加一些约束。 先前的模型表明，磁化云核的早期演化由双极扩散和磁制动所主导，并且云核呈现出一种非平衡的扁平包层形式，最终动态坍缩形成原恒星。 在本文中，我们关注的是在中心原恒星存在之后形成的内部离心支撑盘，并且该盘通过从扁平包层的动力学吸积而增长。 我们估计了旋转、磁化云核内质量壳层坍缩的离心半径。 内部盘的离心半径通过两个表征背景介质的重要参数与它的质量相关：背景旋转速率$\Omb$和背景磁场强度$\Bref$。 我们还重新审视了质量沉积到盘上的速度（质量吸积率）这一问题，并利用几个最近的模型来评论磁化云核中的可能结果。 我们的模型预测，在原恒星演化的非常早期（0类）阶段，将会存在一个显著的离心盘（远大于恒星半径）。 此外，我们在假设星盘系统在大部分质量转移到中心恒星的同时仍保持其质量和角动量守恒的前提下，推导了由于内部扭矩作用而演化时的盘半径上限。 显示英文摘要

摘要： We use magnetic collapse models to place some constraints on the formation and angular momentum evolution of circumstellar disks which are embedded in magnetized cloud cores. Previous models have shown that the early evolution of a magnetized cloud core is governed by ambipolar diffusion and magnetic braking, and that the core takes the form of a nonequilibrium flattened envelope which ultimately collapses dynamically to form a protostar. In this paper, we focus on the inner centrifugally-supported disk, which is formed only after a central protostar exists, and grows by dynamical accretion from the flattened envelope. We estimate a centrifugal radius for the collapse of mass shells within a rotating, magnetized cloud core. The centrifugal radius of the inner disk is related to its mass through the two important parameters characterizing the background medium: the background rotation rate $\Omb$ and the background magnetic field strength $\Bref$. We also revisit the issue of how rapidly mass is deposited onto the disk (the mass accretion rate) and use several recent models to comment upon the likely outcome in magnetized cores. Our model predicts that a significant centrifugal disk (much larger than a stellar radius) will be present in the very early (Class 0) stage of protostellar evolution. Additionally, we derive an upper limit for the disk radius as it evolves due to internal torques, under the assumption that the star-disk system conserves its mass and angular momentum even while most of the mass is transferred to a central star.