论文标题
恒星形成的不同模式II：最初亚临界恒星云的气体积聚阶段
Different Modes of Star Formation II: Gas Accretion Phase of Initially Subcritical Star-Forming Clouds
论文作者
论文摘要
恒星形成的增生阶段在具有初始亚临界质量升级比率的磁性云中进行了研究。我们采用非理想的磁流失动力学模拟，包括双相扩散和欧姆消散。在早期的prestell阶段，质量与频率比率朝着崩溃的临界值升高，在此期间，云芯的角动量通过磁制动大大降低。一旦在核心中形成原恒星，积聚阶段的特征是存在少量的角动量，但在近透明环境中存在大量的磁通量。低角度动量导致非常小（甚至不存在）磁盘和弱流出，而大型磁通量会导致互换不稳定，从而迅速消除了中央区域的通量。早期塌陷阶段的有效磁制动甚至可以导致反向旋转的磁盘和流出，其中磁盘的旋转方向和流出与插入信封的旋转方向相反。具有反旋转磁盘，微小磁盘或不存在的磁盘（直接崩溃）的解决方案是独特的结果，在具有初始亚临界质量质量与频率比的磁偏云中崩溃。
The accretion phase of star formation is investigated in magnetically-dominated clouds that have an initial subcritical mass-to-flux ratio. We employ nonideal magnetohydrodynamic simulations that include ambipolar diffusion and ohmic dissipation. During the early prestellar phase the mass-to-flux ratio rises toward the critical value for collapse, and during this time the angular momentum of the cloud core is reduced significantly by magnetic braking. Once a protostar is formed in the core, the accretion phase is characterized by the presence of a small amount of angular momentum but a large amount of magnetic flux in the near-protostellar environment. The low angular momentum leads to a very small (or even nonexistent) disk and weak outflow, while the large magnetic flux can lead to an interchange instability that rapidly removes flux from the central region. The effective magnetic braking in the early collapse phase can even lead to a counter-rotating disk and outflow, in which the rotation direction of the disk and outflow is opposite to that of the infalling envelope. The solutions with a counter-rotating disk, tiny disk, or nonexistent disk (direct collapse) are unique outcomes that are realized in collapse from magnetically-dominated clouds with an initial subcritical mass-to-flux ratio.
