论文标题
拆开动态时钟。脂肪尾动力踢形状蓝色 - straggler star双峰性
Taking apart the dynamical clock. Fat-tailed dynamical kicks shape the blue-straggler star bimodality
论文作者
论文摘要
在球状簇中,蓝色的straggler恒星比普通恒星重,因此动态摩擦会强烈影响它们。标准化为参考人群的BS的径向分布在一小部分的银河GC中似乎是双峰,核心的密度峰是中间半径的突出避免区域,郊区的密度更高。回避区域似乎位于较大的半径上,主机群群越轻松,充当动态时钟。我们使用一种新方法来计算在动态摩擦和扩散下BSS径向分布的演变。我们在动态摩擦和随机波动力下的平均簇电位中进化了BSS,并使用Mannella Quasi symbletectic方案求解Langevin方程。这相当于一种新的仿真方法,该方法比直接N体代码更快,更简单,但保留其主要特征:扩散由强力(如果不经常)踢。我们计算最初未分类的BSS的径向分布,该BSS归一化为参考总体,随时间的函数。我们追踪其最小值的演变,与回避区域相对应。我们比较从高斯分布提取的踢和使用Holtsmark分布获得的演变。后者是一种脂肪尾分布,可以正确地模拟紧密的重力相遇的效果。我们发现,根据观测值的预期,回避区域随着时间的推移会随着时间的推移而向外移动,只有在使用Holtsmark分布时。因此,近距离相遇的正确表示对于重现系统的动力学至关重要。我们确认并扩展了早期的结果,这些结果表明了动态时钟指示器如何依赖于动态摩擦和由动态接触供电的有效扩散。
In globular clusters, blue straggler stars are heavier than the average star, so dynamical friction strongly affects them. The radial distribution of BSS, normalized to a reference population, appears bimodal in a fraction of Galactic GCs, with a density peak in the core, a prominent zone of avoidance at intermediate radii, and again higher density in the outskirts. The zone of avoidance appears to be located at larger radii the more relaxed the host cluster, acting as a sort of dynamical clock. We use a new method to compute the evolution of the BSS radial distribution under dynamical friction and diffusion. We evolve our BSS in the mean cluster potential under dynamical friction plus a random fluctuating force, solving the Langevin equation with the Mannella quasi symplectic scheme. This amounts to a new simulation method which is much faster and simpler than direct N-body codes but retains their main feature: diffusion powered by strong, if infrequent, kicks. We compute the radial distribution of initially unsegregated BSS normalized to a reference population as a function of time. We trace the evolution of its minimum, corresponding to the zone of avoidance. We compare the evolution under kicks extracted from a Gaussian distribution to that obtained using a Holtsmark distribution. The latter is a fat tailed distribution which correctly models the effects of close gravitational encounters. We find that the zone of avoidance moves outwards over time, as expected based on observations, only when using the Holtsmark distribution. Thus the correct representation of near encounters is crucial to reproduce the dynamics of the system. We confirm and extend earlier results that showed how the dynamical clock indicator depends both on dynamical friction and effective diffusion powered by dynamical encounters.