Impact of protostellar outflow on star formation: effects of the initial cloud mass
Impact of protostellar outflow on star formation: effects of the initial cloud mass
复制标题
DOI：
10.1111/j.1365-2966.2011.20336.x
复制
发表时间：
2011-08
影响因子：
4.8
通讯作者：
M. Machida;Tomoaki Matsumoto
中科院分区：
文献类型：
--
作者：
M. Machida;Tomoaki Matsumoto
用三维电阻磁流体(MHD)模拟研究了原恒星外流对单个云核恒星形成的影响。从恒星前的云核开始，计算恒星的形成过程，直到主吸积阶段结束。在计算中，恒星前星云的质量被参数化。在恒星形成过程中，原恒星的外流是由环绕恒星的圆盘驱动的。流出流也沿横向扩展，直到其宽度与初始云尺度相当，因此流出流具有≳40°的宽张角。结果，原恒星外流卷起了一大部分流入的物质，并将其喷射到星际空间。外流最多可以喷出一半以上的宿主云质量，显著降低恒星形成效率。在初始质量较大的云中，流出功率较强。因此，原恒星外流有效地抑制了大质量星云中恒星的形成效率。在云开始坍塌后，外流明显减弱，并在初始云的几个自由落体时间尺度上消失。恒星诞生前的核心会影响外流的寿命和大小。在主吸积阶段结束时，一个质量相当于原恒星的质量的星际圆盘仍然存在。计算表明，∼26-54%的初始云质量转化为原恒星，∼8%-40%留在星周盘中，而∼8%-49%可被原恒星流出射到星际空间。因此，原恒星外流最大可能会使恒星形成效率降低到∼的50%。
The effects of a protostellar outflow on the star formation in a single cloud core are investigated by three-dimensional resistive magnetohydrodynamic (MHD) simulations. Starting from the pre-stellar cloud core, the star formation process is calculated until the end of the main accretion phase. In the calculations, the mass of the pre-stellar cloud is parametrized. During the star formation, the protostellar outflow is driven by the circumstellar disc. The outflow extends also in the transverse direction until its width becomes comparable to the initial cloud scale, and thus the outflow has a wide opening angle of ≳40°. As a result, the protostellar outflow sweeps up a large fraction of the infalling material and ejects it into the interstellar space. The outflow can eject at most over half of the host cloud mass, significantly decreasing the star formation efficiency. The outflow power is stronger in clouds with a greater initial mass. Thus, the protostellar outflow effectively suppresses the star formation efficiency in a massive cloud. The outflow weakens significantly and disappears in several free-fall time-scales of the initial cloud after the cloud begins to collapse. The natal pre-stellar core influences the lifetime and size of the outflow. At the end of the main accretion phase, a massive circumstellar disc comparable in mass to the protostar remains. Calculations show that ∼26–54 per cent of the initial cloud mass is converted into the protostar and ∼8–40 per cent remains in the circumstellar disc, while ∼8–49 per cent can be ejected into the interstellar space by the protostellar outflow. Therefore, the protostellar outflow can decrease the star formation efficiency to ∼50 per cent at the maximum.