标题： 由星团环境引起的引力不稳定？ - 盘中由相遇引起的角动量转移 显示英文标题

标题： Gravitational Instabilities induced by Cluster Environment? - The encounter-induced angular momentum transfer in discs

摘要： 目标：这项工作的目的在于理解恒星之间的引力相互作用在高密度年轻恒星团中（例如猎户座星云团，ONC）对其原行星盘角动量的影响程度。 方法：结合了两种模拟方式——猎户座星云团中恒星动力学的N体模拟，以及恒星与原行星盘相遇后角动量损失的模拟结果。 结果：研究表明，在恒星与原行星盘的相遇过程中，角动量损失通常大于质量损失，因此剩余盘的比角动量会降低。假设猎户座星云团年龄为1-2百万年，则在昴宿星团高密度区域的盘角动量平均减少15-20%。因此，相遇在这些中心区域的角动量传输中起着重要作用，但并非主导过程。更重要的是，即使在外围区域，角动量损失平均也达到了3-5%。这里显示，3-5%的角动量损失可能足以触发低质量盘中的引力不稳定现象——这是行星系统形成的一个可能前提条件。 显示英文摘要

摘要： AIM:The aim of this work is to understand to what extend gravitational interactions between the stars in high-density young stellar clusters, like the Orion Nebula Cluster (ONC), change the angular momentum in their protoplanetary discs. METHOD:Two types of simulations were combined -- N-body simulations of the dynamics of the stars in the ONC, and angular momentum loss results from simulations of star-disc encounters. RESULTS:It is shown that in a star-disc encounter the angular momentum loss is usually larger than the mass loss, so that the disc remnant has a lower specific angular momentum. Assuming an age of 1-2 Myr for the ONC, the disc angular momentum in the higher density region of the Trapezium is reduced by 15-20% on average. Encounters therefore play an important part in the angular momentum transport in these central regions but are not the dominant process. More importantly, even in the outer cluster regions the angular momentum loss is on average 3-5%. Here it is shown that a 3-5% loss in angular momentum might be enough to trigger gravitational instabilities even in low-mass discs - a possible prerequisite for the formation of planetary systems.