标题： 致密旋转系统的动力学演化：第一篇。两体松弛效应 显示英文标题

标题： The Dynamical Evolution of Dense Rotating Systems: Paper I. Two-Body Relaxation Effects

摘要： 本文及其相关论文研究了密集恒星系统由于双体引力相遇、物理碰撞和恒星演化的影响力而产生的演化过程。 我们的目标是模拟星系最密集的中心，如M32，其恒星密度接近每立方秒差距一百万太阳质量，并可能包含黑洞。 这些系统的Safronov数（恒星结合能与平均恒星动能的无量纲比值）不同于球状星团，这显著增加了物理碰撞相对于引力相遇的重要性。 在本文中，我们仅关注引力相遇。 我们首先证明，使用Hernquist树代码进行的小N模拟结果基本上与多年来对球状星团的研究结果一致。 其次，我们粗略地研究了具有质量分层的旋转系统中的核心坍缩，以将纯粹由双体相遇引起的效应与在更复杂的第二篇论文中看到的效应区分开来。 与之前的研究一致，我们发现其组成粒子遵循Salpeter初始质量函数的系统会通过Spitzer的质量分层不稳定性迅速发生核心坍缩。 所有旋转扁平系统随时间推移显示出扁平度的降低，这与Fokker-Planck计算一致。 一个有趣的新结果涉及模拟器在模拟碰撞系统时无法识别静态中心的已建立问题。 我们发现，在中心凝聚的高质量恒星团块以布朗运动的方式在核心内移动。 显示英文摘要

摘要： This paper, and its companion, investigate the evolution of dense stellar systems due to the influence of two-body gravitational encounters, physical collisions and stellar evolution. Our goal is the simulation of the densest centers of galaxies, like M32, which reach stellar densities near a million solar masses per cubic parsec and which may harbor black holes. These systems have a different Safronov number (the dimensionless ratio of stellar binding energy to mean stellar kinetic energy) than globular clusters, substantially increasing the importance of physical collisions relative to gravitational encounters. In this paper, we focus only on the gravitational encounters. We demonstrate, first, that our simulations with small N with a Hernquist tree code yield results basically in accord with years of effort studying globular clusters. Second, we investigate (crudely) core collapse in rotating systems with mass segregation, to separate out the effects purely due to two-body encounters from those seen in the more complex second paper. Consistent with previous studies, we find that systems whose constituent particles follow the Salpeter initial mass function rapidly undergo core collapse through Spitzer's mass segregation instability. All rotationally flattened systems show a decrease in flattening with time, consistent with Fokker-Planck calculations. An interesting new result concerns the well-established inability of simulators to identify a static center in their simulations of collisional systems. We find that the lump of high mass stars which condenses at the center wanders about the core in Brownian motion.