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

大质量恒星的分布，无论是星团状的还是在场上的，都对它们的形成和星系的演化施加了限制。检查最近的大质量恒星形成地点猎户座星云星团(ONC)中的梯形星团(ONC)的状况和ONC的OB数量，出现了两个差异：i)位于ONC中心的梯形星团，现在包含4个OB恒星系统，预计到现在已经完全动态衰变--II)考虑到ONC的总质量，它应该不再存在。预计大约有40颗OB恒星在其内部形成，但只观察到了10颗。这些问题已经用OB-STAR核心模型进行了研究，该模型由40颗OB-STAR组成，初始空间范围类似于梯形(Pflamm-Altenburg&Kroupa，2006)。虽然这个模型基于一些简化(没有周围的星系势，没有松弛的低质量恒星，没有原始双星和没有物理碰撞)，但它证实了在1Myr之后，所有形成的OB星中只有25%留在ONC中。大多数是通过强烈的动力学碰撞从ONC核心射出的。然而，原始双星AXE一旦被包括在模型中，预计将进一步增加OB-STAR赤字。该项目的目的是改进和扩展ONC现有的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恒星分布的数值数据与OB星表数据进行比较。

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.