论文标题
磁盘星系中条形形成的机制：Apsidal进动的同步
A mechanism of bar formation in disk galaxies: synchronization of apsidal precession
论文作者
论文摘要
我们使用理想化的星系中的无碰撞N体模拟的结果讨论了分离和潮汐磁盘星系中条形形成的机理。 In order to better understand the mechanism, we investigate orbital eccentricities (e), epochs of apocenter passages (t_a), azimuthal angles at t_a (varphi_a), precession rates (Omega_pre), for individual stars, as well as bar strengths represented by relative m=2 Fourier amplitude (A_2) and bar pattern speeds (Omega_bar).主要结果如下。在孤立的磁盘星系中，最初具有不同varphi_a和omega_pre的恒星在几个动态时尺度内可以具有相似的值。在本研究中，varphi_a和omega_pre的这种同步被称为apsidal prepession同步（``APS''），是由重力分支的分支组成的增强强度引起的。首先通过磁盘的局部区域中的AP形成弱种子条（A_2 <0.1），然后由于AP而生长。在条形生长阶段（0.1 <a_2 <0.4），由于从杆上的切向力增加，AP可以更有效地进行，因此它可以进一步增强条形强度。 APS中的这种积极反馈回路是隔离恒星磁盘中条形生长的关键物理机制。由于效率较低的AP，可以在磁盘质量较低的磁盘和/或更高$ Q $参数的磁盘中严重抑制条形。与自发的棒形成相比，由于强烈的潮汐扰动在潮汐条的形成中，AP的进行更快，更有效。
We discuss the mechanism(s) of bar formation in isolated and tidally interacting disk galaxies using the results of idealized collisionless Nbody simulations of the galaxies. In order to better understand the mechanism, we investigate orbital eccentricities (e), epochs of apocenter passages (t_a), azimuthal angles at t_a (varphi_a), precession rates (Omega_pre), for individual stars, as well as bar strengths represented by relative m=2 Fourier amplitude (A_2) and bar pattern speeds (Omega_bar). The main results are as follows. A significant fraction of stars with initially different varphi_a and Omega_pre in an isolated disk galaxy can have similar values within several dynamical timescales. This synchronization of varphi_a and Omega_pre, which is referred to as apsidal precession synchronization (``APS'') in the present study, is caused by the enhanced strength of the tangential component of gravitational force. A weak seed bar (A_2<0.1) is first formed through APS in local regions of a disk, then the bar grows due to APS. In the bar growth phase (0.1<A_2<0.4), APS can proceed more efficiently due to stronger tangential force from the bar so that it can enhance the bar strength further. This positive feedback loop in APS is the key physical mechanism of bar growth in isolated stellar disks. Bar formation can be severely suppressed in disks with lower disk mass fractions and/or higher $Q$ parameters due to much less efficient APS. APS proceeds more rapidly and more efficiently due to strong tidal perturbation in the formation of tidal bars compared to spontaneous bar formation.
