GALACTIC SPIRAL ARMS BY SWING AMPLIFICATION
GALACTIC SPIRAL ARMS BY SWING AMPLIFICATION
复制标题
摆动放大的银河旋臂
DOI：
10.3847/0004-637x/821/1/35
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
E. Kokubo
中科院分区：
文献类型：
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作者：
S. Michikoshi;E. Kokubo
基于Julian&Toomre的摆动放大模型，我们研究了盘状星系中恒星螺旋的形成和结构。我们计算了最大放大模式的俯仰角、波长和放大系数。我们还得到了这些量与周转频率和Toomre‘s Q的函数的拟合公式。随着周转频率的增加，俯仰角和径向波长增大，而方位波长减小。俯仰角和径向波长随Q的增大而增大，而方位波长与Q的依赖关系较弱，放大系数随Q迅速减小。为了验证摆动放大模型，我们进行了局部N体模拟。摆动放大模型的波长和俯仰角与N体模拟的结果吻合较好。在N体模拟中，放大因子对本轮频率的依赖关系与摆动放大模型中的结果基本一致。利用这些结果，我们估计了螺旋臂的数量作为剪切率的函数。当圆盘与晕的质量比一定时，螺旋臂的数目随着剪切速率的增加而增加。
Based on the swing amplification model of Julian & Toomre, we investigate the formation and structure of stellar spirals in disk galaxies. We calculate the pitch angle, wavelengths, and amplification factor of the most amplified mode. We also obtain the fitting formulae of these quantities as a function of the epicycle frequency and Toomre’s Q. As the epicycle frequency increases, the pitch angle and radial wavelength increase, while the azimuthal wavelength decreases. The pitch angle and radial wavelength increase with Q, while the azimuthal wavelength weakly depends on Q. The amplification factor decreases with Q rapidly. In order to confirm the swing amplification model, we perform local N-body simulations. The wavelengths and pitch angle of the swing amplification model are in good agreement with those by N-body simulations. The dependence of the amplification factor on the epicycle frequency in N-body simulations is generally consistent with that in the swing amplification model. Using these results, we estimate the number of spiral arms as a function of the shear rate. The number of spiral arms increases with the shear rate if the disk-to-halo mass ratio is fixed.