The decay of OB-star cores of ONC-type star clusters

大质量恒星的分布，无论是聚集在一起还是在场中，都对它们的形成和星系的演化施加了限制。检查最近的猎户座星云星团（ONC）中的梯形星（Trapezium）和ONC的OB人口的状态，出现了两个差异：i）ONC中心的梯形星（Trapezium），今天包含4个OB恒星系统，预计现在已经完全动态衰变-它应该不再存在ii）考虑到ONC的总质量。大约有40颗OB星在其中形成，但只有10颗被观察到。这些问题已经使用OB星核心模型进行了研究，该模型由40颗OB星组成，其初始空间范围像梯形（Pflamm-Altenburg & Kroupa，2006）。虽然这个模型是基于一些简化（没有周围的星团势，没有低质量恒星的弛豫，没有原始双星和没有物理碰撞），它证实了只有25%的所有形成的OB恒星在100万年后仍然留在ONC中。大多数是通过强烈的动力碰撞从ONC核心射出的。然而，一旦原始双星被纳入模型，预计将进一步增加OB星的赤字。该项目的目的是改进和扩展现有的ONC的OB核心模型，包括原始双星，OB核心恒星和低质量星团恒星之间的两体弛豫，剩余恒星和物理碰撞产生的引力势，并将获得的大尺度OB星分布的数值数据与OB星表的数据进行比较。

The distribution of massive stars, clustered or in the field, imposes constraints on their formation and on the evolution of galaxies. Inspecting the status of the nearest massive-star forming site, the Trapezium in the Orion Nebula cluster (ONC) and the OB population of the ONC, two discrepancies arise: i) The Trapezium at the centre of the ONC, which today contains 4 OB star-systems, is expected to have totally dynamically decayed by now — it should not exist anymore ii) Given the total mass of the ONC. about 40 OB stars are expected to have formed in it but only ten are observed. These problems have been studied using an OB-star core model consisting of 40 OB stars having an initial spatial extent like the Trapezium (Pflamm-Altenburg & Kroupa, 2006). Although this model is based on some simplifications (no surrounding cluster potential, no relaxation with low-mass stars, no primordial binaries and no physical collisions) it confirms that only 25 % of all formed OB stars remain in the ONC after 1 Myr. The majority are shot-out from the ONC core through strong dynamical encounters.Primordial binaries axe, however, expected to increase the OB-star deficit even more once they are included in the modelling. It is the aim of this project to improve and to extend the existing OB-core model of the ONC by including primordial binaries, two-body relaxation between OB-core stars and low-mass cluster stars, the gravitational potential created by the remaining stars and physical collisions, and to compare the obtained numerical data on the wide-scale OB-star distribution with data from OB-star catalogues.