AI 中文总结
该研究通过ROLLIN'系列直接N体模拟，揭示旋转球状星团的形态受多尺度动力学影响，为相关观测关系及异常值提供物理解释，将助力大型测光巡天对球状星团演化的研究。
AI 中文摘要
球状星团（GCs）本质上是具有内部旋转的非球形系统，通常认为旋转是GCs形态的主要驱动因素，但椭率与旋转支撑之间并非简单的一一对应关系，其他多尺度动力学过程也可能有贡献。我们研究旋转GCs的真实模型中形态如何演化，以及其与质量损失、恒星演化、外部潮汐场和两体弛豫等关键物理要素的关联。利用ROLLIN'系列直接N体模拟，我们通过二阶矩张量方法测量模型的本征椭率和三轴度，探究其演化及驱动的物理机制。我们发现，GC早期演化可由内部旋转和速度各向异性驱动的动力学不稳定性主导，形成的类棒结构在首次核心坍缩前后因碰撞效应快速消散；在旋转强、弛豫时间长且受恒星演化影响的星团中，这类棒结构更强且寿命更长（≤800 Myr）。长期来看，星团会向更不扁平和逐渐三轴化的构型演化，尤其在经历更强质量损失、更易被潮汐填充、呈各向同性且旋转支撑更低时。我们的模型为观测到的V/σ-椭率关系提供了物理解释，证明形态可作为GCs动力学状态的可靠示踪剂；初始逆行、致密且倾斜的旋转模型偏离该关系，为观测异常值提供了物理解释，该框架将助力未来大型测光巡天中GCs演化的解读。
英文摘要
Globular clusters (GCs) are inherently non-spherical systems that in many cases show internal rotation. Typically, rotation is considered the main driver of GC morphology; however, the relationship between ellipticity and rotational support is not a simple one-to-one mapping, and other multi-scale dynamical processes may contribute. We investigate how morphology evolves in realistic models of rotating GCs, and how it correlates with key physical ingredients, including mass loss, stellar evolution, external tidal fields, and two-body relaxation. Using the \texttt{ROLLIN'} suite of direct N-body simulations, we measure the intrinsic ellipticity and triaxiality of our models using the second-moment tensor method, and explore their evolution and the physical mechanisms driving them. We find that early GC evolution can be dominated by dynamical instabilities driven by internal rotation and velocity anisotropy, leading to bar-like structures that rapidly erode due to collisional effects around the time of the first core collapse. These bars are stronger and longer-lived ($\lesssim 800,\mathrm{Myr}$) in strongly rotating clusters with longer relaxation times and subject to stellar evolution. In the long term, clusters evolve toward less flattened and gradually triaxial configurations, particularly when they experience stronger mass loss, are more tidally filling and isotropic, and have lower rotational support. Our models provide a physical explanation for the observational $V/σ$--ellipticity relation and demonstrate that morphology can serve as a reliable tracer of the dynamical state of GCs. Initially retrograde, dense, and inclined rotating models deviate from this relation, providing a physical explanation for observational outliers. This framework will aid the interpretation of GC evolution in upcoming large-scale photometric surveys.
CommentsAccepted for publication in A&A. 25 pages, 20 figures
