This paper constructs an analytic form for a triaxial potential that describes the dynamics of a wide variety of astrophysical systems, including the inner portions of dark matter halos, the central regions of galactic bulges, and young embedded star clusters. Specifically, this potential results from a density profile of the form $ρ(m) \propto m^{-1}$, where the radial coordinate is generalized to triaxial form so that $m^2 = x^2/a^2 + y^2/b^2 + z^2/c^2 $. Using the resulting analytic form of the potential, and the corresponding force laws, we construct orbit solutions and show that a robust orbit instability exists in these systems. For orbits initially confined to any of the three principal planes, the motion in the perpendicular direction can be unstable. We discuss the range of parameter space for which these orbits are unstable, find the growth rates and saturation levels of the instability, and develop a set of analytic model equations that elucidate the essential physics of the instability mechanism. This orbit instability has a large number of astrophysical implications and applications, including understanding the formation of dark matter halos, the structure of galactic bulges, the survival of tidal streams, and the early evolution of embedded star clusters.
The dwarf galaxy DDO 47: testing cusps hiding in triaxial halos
我们提出的矮星系DDO 47的HI数据，旨在测试的假设，暗晕三轴性可能会导致非圆运动的旋转曲线最适合的核心晕，即使暗物质晕本质上是尖的。为了寻找所谓的“隐藏”尖点所需的非圆形运动，我们对速度场进行了谐波分解：在DDO 47中，非圆形运动在全球范围内处于2-3 km s $^{-1}$的水平，远远不足以使观测到的旋转曲线与$Λ$ CDM预测相一致。我们的结论是，围绕DDO 47的暗物质晕是真正的核心和尖点不能隐藏的非圆形运动。更多细节显示在Gentile等人（2006，ApJL in press，astro-ph/0506538）中。
Chaos in cuspy triaxial galaxies with a supermassive black hole: a simple toy model
This paper summarises an investigation of chaos in a toy potential which mimics much of the behaviour observed for the more realistic triaxial generalisations of the Dehnen potentials, which have been used to model cuspy triaxial galaxies both with and without a supermassive black hole . The potential is the sum of an anisotropic harmonic oscillator potential, V_o=(1/2)*(a^{2}x^{2}+b^{2}y^{2}+c^{2}z^{2}), and a spherical Plummer potential, V_o=- M_{BH} /(r^{2}+e^{2})^{1/2} with r^{2}=x^{2}+y^{2}+z^{2}. Attention focuses on three issues related to the properties of ensembles of chaotic orbits w…
