论文标题
星系的螺旋臂
The spiral arms of galaxies
论文作者
论文摘要
星系螺旋臂的最重要理论是基于lin-shu色散关系的密度波理论。但是，密度波随组速度向内部林布拉德共振而移动，并且往往会消失。已经提出了各种补充螺旋波的机制。非线性效应在内部和外部林布拉德共振和旋律附近起重要作用。支撑螺旋臂的轨道是正常星系中的进攻椭圆，延伸至4/1共振。另一方面，在禁止的星系中，螺旋臂沿着杆末端的不稳定周期轨道的歧管延伸，它们由混沌轨道组成。但是，可以通过分析发现这些混沌轨道。
The most important theory of the spiral arms of galaxies is the density wave theory based on the Lin-Shu dispersion relation. However, the density waves move with the group velocity towards the inner Lindblad resonance and tend to disappear. Various mechanisms to replenish the spiral waves have been proposed. Nonlinear effects play an important role near the inner and outer Lindblad resonances and corotation. The orbits supporting the spiral arms are precessing ellipses in normal galaxies that extend up to the 4/1 resonance. On the other hand, in barred galaxies the spiral arms extend along the manifolds of the unstable periodic orbits at the ends of the bar and they are composed of chaotic orbits. However these chaotic orbits can be found analytically.
