Structure and Stability of Cuspy Triaxial Galaxies

AST-0070809 Kandelman，亨利E.尖状三轴星系的结构和稳定性本项目的目标是构造尖状椭圆星系和早型星系球的三轴分布函数。这将涉及从经典天体力学，现代非线性动力学和统计力学，以及数值算法，如修改Schwartzschild的DF建设技术的技术集成。 它的目的是回答这个问题：什么是DF和三轴星系的表面密度分布之间的连接，以及在这方面的混乱的影响是什么，或者是初始条件的表面密度分布的遗迹？最近的高分辨率观测表明，许多（也许是大多数）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，对于尖点不是太陡的星系，经常有证据表明适度偏离轴对称。然而，理论上的争论，并得到数值研究的证实，强烈地表明，在一个尖形的，非轴对称的星系中的许多恒星会出现混沌运动。直到最近，这一领域的几乎所有工作都完全忽略了这种混乱可能产生的影响。该项目将探索这种混沌对星系结构和演化的物理影响，特别侧重于确定潜在的可观测特征。要解决的问题包括以下几点：1。是否合理的模型，这样的星系是在一个时间无关的统计平衡，或将一个预期的尖形非轴对称星系应该表现出系统的演化效应超过天文学有趣的时间尺度？2.这些星系对与其他相对较近的星系存在相关的低振幅引力不规则性有多敏感？3.这样一个星系将如何应对与一个非常接近的星系的碰撞或近距离接触？这些工作的大部分涉及到物理学家和应用数学家在过去30年中发展起来的思想的应用，这些思想在实验室中得到了反复的证实。然而，星系背景下出现的一个重要新特征是混沌是自洽产生的：在大多数实验室实验中，混沌是由作用于被探测系统的一些外部刺激触发的。当考虑一个星系时，人们会遇到这样一种情况，即混沌是由星系本身的物质所引起的引力引起的。该项目的资金由美国国家科学基金会的河外天文宇宙学计划（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).***