杆和三轴椭球轨道结构的统一框架
A unified framework for the orbital structure of bars and triaxial ellipsoids
摘要：
我们研究了一个大的随机样本的轨道在自洽模拟N体酒吧。条形图中的轨道可以通过视觉和基于频率分析的新自动轨道分类方法进行分类。著名的x1轨道族起源于与静止和旋转三轴椭球中的盒轨道相同的母轨道。然而，只有一小部分的棒轨道（约4%）像它们的周期母轨道一样主要是逆时针运动。大多数从x1轨道产生的棒轨道在棒坐标系中几乎没有净角动量，这使得它们等价于旋转三轴势中的盒轨道。一小部分棒轨道（约7%）是长轴管，其行为与三轴椭球中的长轴管完全相同：由于科里奥利力，它们围绕中轴倾斜，倾斜的方向由它们围绕长轴的角动量的符号决定。在纯棒模型中，没有发现以逆周期x2轨道为母体的轨道，但发现了以逆周期x4轨道为母体的短轴管轨道，其数量约为2%.当一个代表超大质量黑洞（SMBH）的中心质点在棒中心旋转生长时，那些位于SMBH附近的轨道被转换成旋进开普勒轨道（PKO），它们属于相同的主要族（短轴管、长轴管和盒）以较大半径占据杆。在SMBH的生长过程中，质量的流入和角动量的向外输运将一些x1和长轴管轨道转变为短轴管轨道。这项研究具有重要的意义，未来的尝试，以限制质量的SMBHs在棒星系使用基于轨道的方法，如史瓦西轨道叠加方案和了解所观察到的功能在棒星系。
英文摘要：
We examine a large random sample of orbits in self-consistent simulations of N-body bars. Orbits in the bars are classified both visually and with a new automated orbit classification method based on frequency analysis. The well known prograde x1 orbit family originates from the same parent orbit as the box orbits in stationary and rotating triaxial ellipsoids. However only a small fraction of bar orbits ~4% have predominately prograde motion like their periodic parent orbit. Most bar orbits arising from the x1 orbit have little net angular momentum in the bar frame making them equivalent to box orbits in rotating triaxial potentials. A small fraction of bar orbits (~7%) are long axis tubes that behave exactly like those in triaxial ellipsoids:they are tipped about the intermediate-axis due to the Coriolis force, with the sense of tipping determined by the sign of their angular momentum about the long axis. No orbits parented by prograde periodic x2 orbits are found in the pure bar model, but a tiny population (~2%) of short axis tube orbits parented by retrograde x4 orbits are found. When a central point mass representing a supermassive black hole (SMBH) is grown adiabatically at the center of the bar, those orbits that lie in the immediate vicinity of the SMBH are transformed into precessing Keplerian orbits (PKOs) which belong the same major families (short axis tubes, long axis tubes and boxes) occupying the bar at larger radii. During the growth of a SMBH the inflow of mass and outward transport of angular momentum transforms some x1 and long axis tube orbits into prograde short axis tubes. This study has important implications for future attempts to constrain the masses of SMBHs in barred galaxies using orbit based methods like the Schwarzschild orbit superposition scheme and for understanding the observed features in barred galaxies.
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