无碰撞N体模拟中的径向轨道不稳定性
The Radial Orbit Instability in Collisionless N-Body Simulations
摘要：
使用一套自引力，无碰撞的N体模型，我们系统地探索了一个参数空间的发病和行为的径向轨道不稳定性（ROI），其强度是衡量的模型的系统轴比。我们表明，两个初始条件的组合，即速度各向异性和维里比，确定是否系统将进行ROI和究竟如何三轴的系统将成为。第三个初始条件，密度分布的径向形状，起着较小但明显的作用。关于ROI的动态发展，不稳定性a）在系统坍缩到其最紧凑的配置之后开始，并且b）当大多数粒子具有径向各向异性轨道而缺乏中心集中的各向同性轨道时，发展最快。我们认为，这是进一步的证据表明，自我加强扭矩的发病的ROI的关键。我们的研究结果支持这样的想法，即一个单独的轨道不稳定性在停止投资回报率发挥了作用。
英文摘要：
Using a suite of self-gravitating, collisionless N-body models, we systematically explore a parameter space relevant to the onset and behavior of the radial orbit instability (ROI), whose strength is measured by the systemic axis ratios of the models. We show that a combination of two initial conditions, namely the velocity anisotropy and the virial ratio, determines whether a system will undergo ROI and exactly how triaxial the system will become. A third initial condition, the radial shape of the density profile, plays a smaller, but noticeable role. Regarding the dynamical development of the ROI, the instability a) begins after systems collapse to their most compact configuration and b) evolves fastest when a majority of the particles have radially anisotropic orbits while there is a lack of centrally-concentrated isotropic orbits. We argue that this is further evidence that self-reinforcing torques are the key to the onset of the ROI. Our findings support the idea that a separate orbit instability plays a role in halting the ROI.
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