Structure and Stability of Cuspy Triaxial Galaxies

Ast-0070809Kandrup，Henry E.Cuspy三轴星系的结构和稳定性这个项目的目标是为尖顶椭圆星系和早期类型的凸起构造三轴分布函数(DFS)。这将涉及整合经典天体力学、现代非线性动力学和统计力学的技术，以及数值算法，例如修改Schwartzschild的DF构造技术。它的目的是回答这个问题：在三轴星系中，df和表面密度分布之间有什么联系，在这方面混沌的影响是什么，或者表面密度分布是初始条件的遗迹吗？最近的高分辨率观测表明，许多(也许大多数)椭圆星系有一个明显的密度尖点，可能与超大质量黑洞的存在有关；此外，对于尖点不太陡峭的星系，经常有证据表明它偏离了轴对称。然而，得到数值研究证实的理论论证有力地表明，在一个尖峰的非轴对称星系中，许多恒星将表现出混沌运动。直到最近，这一领域的几乎所有工作都完全忽视了这种混乱可能产生的影响。这个项目将探索这种混乱对星系结构和演化的物理影响，特别关注确定潜在的可观察到的特征。需要解决的问题包括：1.将这样的星系模拟为处于与时间无关的统计平衡状态是否合理，或者人们是否可以预测，尖尖的非轴对称星系应该在天文上有趣的时间尺度上表现出系统的演化效应？2.这样的星系对与其他相对较近的星系的存在有关的低幅度引力异常的敏感性有多大？3.这样的星系将如何应对与非常近的星系的碰撞或近距离接触？这项工作的大部分涉及到物理学家和应用数学家在过去30年里提出的并在实验室反复得到证实的思想的应用。然而，在星系背景下出现的一个重要的新特征是，混沌是自我一致地产生的：在大多数实验室实验中，混沌是由一些外部刺激作用于被探测的系统而触发的。当考虑一个星系时，人们会面临这样一种情况，即混沌是由与星系本身中的物质相关的引力引起的。该项目的资金由NSF河外天文与宇宙学计划(AST/EXC)提供。*

AST-0070809Kandrup, Henry E.Structure and Stability of Cuspy Triaxial GalaxiesThe goal of this project is to construct triaxial distribution functions (DFs) for cuspy elliptical galaxies and early-type bulges. This will involve the integration of techniques from classical celestial mechanics, modern nonlinear dynamics and statistical mechanics, as well as numerical algorithms, such as modifications to Schwartzschild's technique for DF construction. It aims to answer the question: What is the connection between the DF and the surface density profiles in triaxial galaxies, and what is the influence of chaos in this connection or are the surface density profiles relics of initial conditions?Recent high resolution observations indicate that many (perhaps most) elliptical galaxies have a pronounced density cusp, possibly associated with the presence of a supermassive black hole; in addition, for galaxies where the cusp is not too steep, there is often evidence for moderate deviations from axisymmetry. However, theoretical arguments, corroborated by numerical investigations, suggest strongly that many of the stars in a cuspy, nonaxisymetric galaxy willexhibit chaotic motions. Until very recently, almost all work in this area has completely ignored the possible effects of this chaos. This project will explore the physical implications of this chaos on the structure and evolution of galaxies, with particular focus on determining potentially observable signatures. Questions to be addressed include the following: 1. Is it reasonable to model such galaxies as being in a time-independent statistical equilibrium, or would one anticipate that cuspy nonaxisymmetric galaxies should exhibit systematic evolutionary effects over astronomically interesting time scales? 2. How susceptible are such galaxies towards low amplitude gravitational irregularities associated with the presence of other comparatively nearby galaxies? 3. How will such a galaxy respond to a collision or close encounter with a very nearby galaxy? Much of this work involves applications of ideas which have been developed by physicists and applied mathematicians over the past thirty years and which have been confirmed repeatedly in the laboratory. However, an important new feature arising in the context of galaxies is that the chaos is generated self-consistently: In most laboratory experiments, chaos is triggered by some external stimulus acting on the system being probed. When considering a galaxy one is confronted with a situation where the chaos is induced by the gravity associated with the matter in the galaxy itself. Funding for this project is provided by the NSF program for Extragalactic Astronomy & Cosmology (AST/EXC).***