发表机构
Instituto Nacional de Astrofísica, Óptica y Electrónica; Universidad Mariana（国家天体物理学、光学和电子学研究所; 马里亚纳大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文提出基于冻结势与傅里叶频率分析的新方法，识别盘状星系棒中x1和x2轨道族，精确追踪棒性质演化，揭示密度分布各向异性及棒增长与混沌、角动量转移的关联。
AI 中文摘要
棒状结构是盘状星系中最显著的动力学结构之一，然而其长期演化以及维持它们的轨道族仍仅被部分理解。在本工作中，我们引入了一种基于冻结势与粒子轨迹傅里叶分析相结合的新方法，用于在自洽N体模拟中识别规则轨道和粘性轨道。该方法使我们能够分离出属于x1族（直接与棒相关）和x2族（与次级垂直结构相关）的粒子。跨多个快照追踪这些轨道，使我们能够量化棒的关键性质（包括其质量分数、半轴和密度分布）的时间演化。与已确立的常用诊断方法相比，我们的方法在匹配傅里叶棒强度参数A2的时间行为方面提供了最接近的结果，同时提供了傅里叶方法无法提供的直接动力学解释和完整三维表征。我们的分析进一步揭示，描述棒密度分布的指数nx、ny和nz是各向异性的，且很少等于Ferrers分布中假设的典型值n=2，这凸显了标准解析近似的局限性。我们还发现棒增长、轨道混沌性和角动量再分布之间存在强相关性，棒既充当角动量转移的汇，也充当其驱动者。对分析的两个模型的比较表明，快速形成的棒比逐渐增长的棒更弱且更不稳定。总之，我们的方法为将轨道结构与棒状星系的动力学演化联系起来提供了一个稳健的框架。
英文摘要
Bars are among the most prominent dynamical structures in disc galaxies, yet their long-term evolution and the orbital families that sustain them remain only partially understood. In this work, we introduce a new methodology based on frozen potentials combined with Fourier analysis of particle trajectories to identify regular and sticky orbits in self-consistent $N$-body simulations. This approach allows us to isolate particles belonging to the $x_1$ family, directly associated with the bar, and the $x_2$ family, linked to a secondary perpendicular structure. Tracking these orbits across multiple snapshots enables us to quantify the time evolution of key bar properties, including its mass fraction, semi-axes, and density profile. Compared with established used diagnostics, our method provides the closest match to the temporal behaviour of the Fourier bar-strength parameter $A_2$, while offering a direct dynamical interpretation and full three-dimensional characterization that Fourier-based approaches cannot provide. Our analysis further reveals that the indices $n_x$, $n_y$, and $n_z$ describing the bar density distribution are anisotropic and rarely equal to the canonical $n=2$ assumed in Ferrers profiles, highlighting the limitations of standard analytical approximations. We also find strong correlations between bar growth, orbital chaoticity, and angular momentum redistribution, with the bar acting both as a sink and as a driver of angular momentum transfer. A comparison between the two models analysed shows that rapidly forming bars are weaker and less stable than those that grow more gradually. Altogether, our methodology provides a robust framework for linking orbital structure to the dynamical evolution of barred galaxies.
Comments19 pages, 23 figures, accepted for publication in MNRAS
