The dynamical evolution of Taurus-Auriga-type aggregates
The dynamical evolution of Taurus-Auriga-type aggregates
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金牛座-御夫座型聚合体的动态演化
DOI：
10.1046/j.1365-2966.2003.06645.x
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发表时间：
2003
影响因子：
4.8
通讯作者：
J. Bouvier
中科院分区：
文献类型：
--
作者：
P. Kroupa;J. Bouvier
金牛座-御夫座（TA）分子云中的星星形成正在产生富含双星的聚集体，在一个没有大质量恒星的区域内，最多包含几十个系统。这种环境与另一个被充分研究的恒星形成事件非常不同，该事件产生了猎户座星云团（ONC）。ONC在一个PC的区域内包含数千个系统，包括大质量恒星。这两种环境之间的差异已经被发现，值得注意的是，ONC的双星比例明显小于TA，但每颗星星孤立的棕矮星（BD）数量明显多于TA。本项目的目的是调查这些差异是否可以单独通过恒星动力学演化来解释。恒星动力学的问题是非常相关的，因为密集的环境破坏了释放BD同伴的双星，可能导致TA和ONC人口之间的差异。在这里，一系列高精度的N体模型的TA类嵌入式聚集体，假设标准的参考恒星形成模型的输入人口，根据该恒星和BD形式具有相同的运动学，空间和二进制属性。在对聚集体的一般演化进行讨论之后，我们发现二元种群实际上大部分是未演化的。因此，TA型星星的形成不可能显著地增加银河系的人口。标准模型导致BD跟踪恒星分布，除了高速尾（v >1 km/s），这导致单个BD的空间分布更广泛。然而，缓慢移动的BD保留了很高的二元比例，这是一个重要的观察诊断测试对胚胎喷射假说。有关国际货币基金组织和双星轨道分布函数的推论在两个附带的文件与有用的影响星星形成和可能的起源BD。
Star formation in the Taurus–Auriga (TA) molecular clouds is producing binary-rich aggregates containing at most a few dozen systems within a region spanning one pc without massive stars. This environment is very different to another well-studied starforming event which produced the Orion Nebula cluster (ONC). The ONC contains a few thousand systems within a region of one pc including massive stars. Differences between these two environments have been found. Notably, the ONC has a significantly smaller binary proportion but a significantly larger number of isolated brown dwarfs (BDs) per star than TA. The aim of the present project is to investigate if these differences can be explained through stellar-dynamical evolution alone. The stellar-dynamical issue is very relevant because dense environments destroy binaries liberating BD companions, possibly leading to the observed difference between the TA and ONC populations. Here a series of high-precision N body models of TA-like embedded aggregates are presented, assuming the standard reference star-formation model for the input populations according to which stars and BDs form with the same kinematical, spatial and binary properties. After a discussion of the general evolution of the aggregates, it is shown that the binary population indeed remains mostly unevolved. Therefore, TA-type star formation cannot have added significantly to the Galactic-field population. The standard model leads to BDs tracing the stellar distribution, apart from a high-velocity tail (v >1 km/s) which leads to a more widely distributed spatial distribution of single BDs. The slow-moving BDs, however, retain a high binary proportion, this being an important observational diagnostic for testing against the embryo-ejection hypothesis. Inferences about the IMF and the binarystar orbital distribution functions are made in two accompanying papers with useful implications for star formation and the possible origin of BDs.