Unstable Disk Galaxies. II. The Origin of Growing and Stationary Modes
Unstable Disk Galaxies. II. The Origin of Growing and Stationary Modes
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不稳定的盘状星系。
DOI：
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发表时间：
2008
期刊：
影响因子：
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通讯作者：
M. A. Jalali
中科院分区：
文献类型：
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作者：
M. A. Jalali
我分解的恒星盘的不稳定的增长模式，其傅立叶分量和共振的上下文中的不稳定性的物理机制。当平衡分布函数是轨道角动量的非均匀函数时，恒星被捕获到共转共振中会使圆盘角动量不平衡，并触发增长的棒和螺旋模式。然后，恒星盘可以通过非共振恒星的响应恢复其角动量平衡。我进行了一个完整的分析轨道结构对应的每个傅立叶分量的径向角和货车坎彭模式，这构成了一个连续的家庭发生的数学条件。我讨论了不稳定模式的离散性和允许的模式速度，并认为模式增长是饱和的，由于共振重叠机制。如果共转和内林德布拉德共振共存并竞争捕获一组恒星，则个体生长模式也可以被抑制。基于这一机制，我表明，自洽无标度盘具有足够的非圆轨道分布下的扰动角波数m > 1应该是稳定的。我还推导出一个标准的稳定性对非轴对称激励的恒星盘。
I decompose the unstable growing modes of stellar disks to their Fourier components and present the physical mechanism of instabilities in the context of resonances. When the equilibrium distribution function is a nonuniform function of the orbital angular momentum, the capture of stars into the corotation resonance imbalances the disk angular momentum and triggers growing bar and spiral modes. The stellar disk can then recover its angular momentum balance through the response of nonresonant stars. I carry out a complete analysis of orbital structure corresponding to each Fourier component in the radial angle and present a mathematical condition for the occurrence of van Kampen modes, which constitute a continuous family. I discuss the discreteness and allowable pattern speeds of unstable modes and argue that the mode growth is saturated due to the resonance overlapping mechanism. An individual growing mode can also be suppressed if the corotation and inner Lindblad resonances coexist and compete to capture a group of stars. Based on this mechanism, I show that self-consistent scale-free disks with a sufficient distribution of noncircular orbits should be stable under perturbations of angular wavenumber m > 1. I also derive a criterion for the stability of stellar disks against nonaxisymmetric excitations.