Resonant Thickening of Disks by Small Satellite Galaxies
Resonant Thickening of Disks by Small Satellite Galaxies
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DOI：
10.1086/306280
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发表时间：
1998-05
期刊：
影响因子：
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通讯作者：
J. Sellwood;R. W. Nelson;S. Tremaine
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文献类型：
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作者：
J. Sellwood;R. W. Nelson;S. Tremaine
我们研究了由于小卫星的吸积而引起的星系盘的垂直加热和增厚。我们的模拟仅限于轴对称，这在很大程度上消除了目标星系的数值演化，但这要求卫星的轨迹沿着目标的对称轴。我们发现卫星对盘状恒星的直接加热并不重要，因为卫星的引力摄动在与垂直恒星轨道共振的频率上功率很小。这颗卫星对盘的破坏很小，直到它衰减的轨道共振地激发出大规模的盘弯曲波。弯波可以通过光晕或内部波粒共振的动力摩擦产生阻尼；我们发现波粒共振主导了阻尼。因此，主要的垂直加热机制是盘内与恒星轨道共振时弯曲波的耗散。因此，能量可以储存在离卫星撞击点一定距离的地方。一颗紧密结合的卫星产生的净热量可能是可观的，但在能够激发弯曲波之前被潮汐破坏的卫星不会使圆盘变厚。
We study the vertical heating and thickening of galaxy disks due to accretion of small satellites. Our simulations are restricted to axial symmetry, which largely eliminates numerical evolution of the target galaxy, but which requires the trajectory of the satellite to be along the symmetry axis of the target. We find that direct heating of disk stars by the satellite is not important, because the satellite's gravitational perturbation has little power at frequencies resonant with the vertical stellar orbits. The satellite does little damage to the disk until its decaying orbit resonantly excites large-scale disk bending waves. Bending waves can damp through dynamical friction from the halo or internal wave-particle resonances; we find that wave-particle resonances dominate the damping. The principal vertical heating mechanism is therefore dissipation of bending waves at resonances with stellar orbits in the disk. Energy can thus be deposited some distance from the point of impact of the satellite. The net heating from a tightly bound satellite can be substantial, but satellites that are tidally disrupted before they are able to excite bending waves do not thicken the disk.