arXiv 1405.63452014-05-24astro-ph.GA

大型设计螺旋的垂直结构与运动学

The Vertical Structure and Kinematics of Grand Design Spirals

Victor P. Debattista

备注：: Letter to MNRAS, in press
DOI：: 10.1093/mnrasl/slu069

摘要：

我们使用一个N体模拟来研究螺旋的3-D密度分布，以及由此产生的恒星垂直速度。相对于圆盘的旋转，螺旋的峰值密度的相位远离中平面，在中平面处。此外，在固定的半径的密度分布是方位倾斜的，具有较浅的斜率的拖尾侧内共转和切换到较浅的领先侧超过共转。这些螺旋导致了非零的平均垂直速度，高达~10 - 20 km/s，与最近在银河系中的观测结果一致。<V_z><V_z>当恒星进入螺旋时，垂直方向的运动是压缩的（朝向中平面），而当它们离开螺旋时，垂直方向的运动是膨胀的（远离中平面）。由于恒星是从正转外的前侧和正转内的后侧进入螺旋，因此膨胀和压缩运动的相对相位在正转时交换。此外，由于恒星总是在密度梯度较浅的一侧进入螺旋，在较陡的一侧离开，因此膨胀运动大于压缩运动。

英文摘要：

We use an N-body simulation to study the 3-D density distribution of spirals, and the resulting stellar vertical velocities. Relative to the disc's rotation, the phase of the spiral's peak density away from the mid-plane trails that at the mid-plane. In addition, at fixed radius the density distribution is azimuthally skewed, having a shallower slope on the trailing side inside corotation and switching to shallower on the leading side beyond corotation. The spirals induce non-zero average vertical velocities, <V_z>, as large as <V_z> ~ 10-20 km/s, consistent with recent observations in the Milky Way. The vertical motions are compressive (towards the mid-plane) as stars enter the spiral, and expanding (away from the mid-plane) as they leave it. Since stars enter the spiral on the leading side outside corotation and on the trailing side within corotation, the relative phase of the expanding and compressive motions switches sides at corotation. Moreover, because stars always enter the spiral on the shallow density gradient side and exit on the steeper side, the expanding motions are larger than the compressing motions.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

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英文摘要：

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