In order to address the question of whether spiral disturbances in galaxy discs are gravitationally coupled to the halo, we conduct simulations of idealized models of disc galaxies. We compare growth rates of spiral instabilities in identical mass models in which the halo is held rigid or is represented by particles drawn from an equilibrium distribution function. We examine cases of radial and azimuthal bias in the halo velocity ellipsoid in one of our models, and an isotropic velocity distribution in both. We find at most marginal evidence for an enhanced growth rate of spiral modes caused by a halo supporting response. We also find evidence for very mild dynamical friction between the spiral disturbance and the halo. We offer an explanation to account for the different behaviour between spiral modes and bar modes, since earlier work had found that bar instabilities became significantly more vigorous when a responsive halo was substituted for an equivalent rigid mass distribution. The barely significant differences found here justify the usual simplifying approximation of a rigid halo made in studies of spiral instabilities in galaxies.

中文翻译：

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螺旋不稳定性：与活晕几乎没有相互作用

为了解决星系盘中的螺旋扰动是否与光晕引力耦合的问题，我们对盘状星系的理想模型进行了模拟。我们比较了相同质量模型中螺旋不稳定性的增长率，其中光环保持刚性或由从平衡分布函数中提取的粒子表示。我们在我们的一个模型中检查了晕速度椭球中径向和方位角偏差的情况，以及两者中的各向同性速度分布。我们至多发现了由光环支持响应引起的螺旋模式增长率提高的边缘证据。我们还发现了螺旋扰动和光晕之间非常温和的动态摩擦的证据。我们提供解释来解释螺旋模式和条模式之间的不同行为，因为早期的工作发现，当用响应晕圈代替等效的刚性质量分布时，棒的不稳定性会变得更加剧烈。这里发现的几乎没有显着差异证明了在研究星系中的螺旋不稳定性时通常对刚性晕进行简化近似是正确的。