A highly abnormal massive star mass function in the Orion Nebula cluster and the dynamical decay of trapezium systems
A highly abnormal massive star mass function in the Orion Nebula cluster and the dynamical decay of trapezium systems
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猎户座星云团中高度异常的大质量恒星质量函数和梯形系统的动力学衰变
DOI：
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发表时间：
2006
期刊：
影响因子：
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通讯作者：
P. Kroupa
中科院分区：
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作者：
J. Pflamm;P. Kroupa
猎户座星云星团（ONC）似乎是不寻常的两个理由：观察到的整个ONC的OB星星座和其中心的四边形意味着一个时间尺度的问题，给出了年龄的四边形，和初始质量函数（IMF）的问题，整个OB星星人口在ONC。根据梯形的穿越时间估计，它现在应该已经完全动态衰减了。此外，结合ONC质量的下限与标准IMF，我们发现ONC应该至少形成了约40颗重于5 M质量的恒星，而实际观测到的只有10颗。使用N体实验，我们（i）确认预期的不稳定性的梯形和（ii）表明，开始与一个紧凑的OB星配置约40颗恒星的数量观测到OB星后，1百万年内1 pc半径和紧凑的斜方星配置可以复制。这两个经验的限制，从而支持我们的估计40个初始OB星的集群。有趣的是，ONC的一个更进化的版本类似于上天蝎座OB协会。用新的C程序CATENA，通过链多重正则化方法积分运动方程，进行了N体实验。此外，我们提出了一个新的数值公式的IMF。
The Orion Nebula cluster (ONC) appears to be unusual on two grounds: the observed constellation of the OB stars of the entire ONC and its Trapezium at its centre implies a time-scale problem given the age of the Trapezium, and an initial mass function (IMF) problem for the whole OB star population in the ONC. Given the estimated crossing time of the Trapezium, it ought to have totally dynamically decayed by now. Furthermore, by combining the lower limit of the ONC mass with a standard IMF it emerges that the ONC should have formed at least about 40 stars heavier than 5 M ⊙ while only 10 are observed. Using the N-body experiments we (i) confirm the expected instability of the Trapezium and (ii) show that beginning with a compact OB-star configuration of about 40 stars both the number of observed OB stars after 1 Myr within 1 pc radius and a compact trapezium configuration can be reproduced. These two empirical constraints thus support our estimate of 40 initial OB stars in the cluster. Interestingly, a more-evolved version of the ONC resembles the Upper Scorpius OB association. The N-body experiments are performed with the new C-code CATENA by integrating the equations of motion using the chain-multiple-regularization method. In addition, we present a new numerical formulation of the IMF.