旋涡星系中恒星速度椭球的形状和取向
Shape and orientation of stellar velocity ellipsoids in spiral galaxies
摘要：
我们提出了一个数值研究的恒星速度分布在恒星盘已开发的饱和，双臂螺旋结构的属性。我们遵循的螺旋结构的增长深入到非线性政权通过解决玻尔兹曼矩方程到二阶。采用薄盘近似，我们将恒星速度分布的研究限制在恒星盘面上。我们发现，恒星旋臂的外（凸）边缘的特点是独特的性能的恒星速度椭球，这使得他们不同于大多数其他星系区域。特别是在旋臂外缘附近，恒星速度椭球的最小主轴与最大主轴的比值σ_1：σ_2会变得异常小（与圆盘的其他部分相比）。此外，epicpherical近似未能重现在这些地区的切向与径向速度分散的比例。恒星速度分布的这些特殊性质是由恒星的大尺度非圆运动引起的，而这种运动又是由恒星旋臂的非轴对称引力场触发的。顶点偏差的大小似乎与螺旋形恒星密度扰动的幅度在全球范围内相关。然而，在局部情况下，在顶点偏差和密度扰动之间没有简单的相关性。（摘要删节）。
英文摘要：
We present a numerical study of the properties of the stellar velocity distribution in stellar discs which have developed a saturated, two-armed spiral structure. We follow the growth of the spiral structure deeply into the non-linear regime by solving the Boltzmann moment equations up to second order. By adopting the thin-disc approximation, we restrict our study of the stellar velocity distribution to the plane of the stellar disc. We find that the outer (convex) edges of stellar spiral arms are characterized by peculiar properties of the stellar velocity ellipsoids, which make them distinct from most other galactic regions. In particular, the ratio σ_1:σ_2 of the smallest versus largest principal axes of the stellar velocity ellipsoid can become abnormally small (as compared to the rest of the disc) near the outer edges of spiral arms. Moreover, the epicycle approximation fails to reproduce the ratio of the tangential versus radial velocity dispersions in these regions. These peculiar properties of the stellar velocity distribution are caused by large-scale non-circular motions of stars, which in turn are triggered by the non-axisymmetric gravitational field of stellar spiral arms. The magnitude of the vertex deviation appears to correlate globally with the amplitude of the spiral stellar density perturbations. However, locally there is no simple correlation between the vertex deviation and the density perturbations. (Abstract abridged).
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