AI 中文总结
本文以HH 212、HH 211和B335为对象，用Terebey-Shu-Cassen模型结合适度磁效应，研究恒星形成早期从核到盘尺度的角动量演化，发现由内向外坍缩场景可合理描述该演化。
AI 中文摘要
本文利用HH 212、HH 211和B335三个原恒星系统，研究恒星形成早期从核到盘尺度的角动量演化。观测显示，比角动量在核尺度上遵循幂律依赖关系，在更小半径处转变为近似恒定值，表明内包层存在动力学坍缩。本文采用Shu（1977）的由内向外坍缩解及其旋转扩展的Terebey-Shu-Cassen模型，通过扁平磁化核引入适度磁效应来模拟该行为。研究发现，三个源的观测角动量轮廓与由内向外坍缩场景大致一致，坍缩区域的比角动量近似守恒。推断的坍缩年龄和质量吸积率得到的中心吸积总质量，与运动学推导的中心质量大致相符，允许部分物质被喷流和星风抛出。预测的典型半径处中平面密度（含磁扁平化效应）也与观测估计一致。尽管三个系统的比角动量数值差异很大，但表现出相似的角动量演化模式。特别是B335的小盘可由其较低的初始比角动量自然解释，不过无法排除磁制动或不同初始条件等其他解释。这些结果表明，带有适度磁修正的由内向外坍缩，可为恒星形成早期从核到盘尺度的角动量演化提供合理的一阶描述。
英文摘要
I investigate the angular momentum evolution from core to disk scales in the early phase of star formation using three protostellar systems: HH 212, HH 211, and B335. Observations show that the specific angular momentum follows a power-law dependence at core scales and transitions to an approximately constant value at smaller radii, indicating dynamical collapse in the inner envelope. I model this behavior using the inside-out collapse solution of Shu (1977) and its rotating extension, the Terebey-Shu-Cassen model, including modest magnetic effects through a flattened, magnetized core. I find that the observed angular momentum profiles in all three sources are broadly consistent with an inside-out collapse scenario with approximate conservation of specific angular momentum in the collapsing region. The inferred collapse ages and mass infall rates yield total masses accreted onto the center that are broadly consistent with the central masses derived from kinematics, allowing for a fraction of the material to be ejected by jets and winds. The predicted midplane densities at typical radii, including the effect of magnetic flattening, are also consistent with observational estimates. The three systems exhibit a similar pattern of angular momentum evolution despite large differences in the magnitude of their specific angular momentum. In particular, the small disk in B335 can be naturally explained by its lower initial specific angular momentum, although alternative explanations, such as magnetic braking or different initial conditions, cannot be excluded. These results suggest that inside-out collapse, with modest magnetic modification, provides a plausible first-order description of angular momentum evolution from core to disk scales in the early phase of star formation.
Comments16 pages, 2 figures
