arXiv 1111.50132011-11astro-ph.GAastro-ph.SR

再论潮汐尾的结构

摘要：

我们研究了从星团中逃逸出来的恒星的周转运动。使用streaklines，我们可视化的逃逸恒星的路径，并显示如何周转运动导致过-和不足的潮汐尾星团的圆形和偏心轨道上移动的星系。此外，我们调查的集群质量上的潮汐尾巴的效果，通过显示，它们的结构是更好地匹配时，集群质量的扰动效应。通过调整streaklines的N体计算的结果，我们可以准确，快速地再现所有观察到的子结构，特别是条纹的功能，经常发现在模拟中可能会被解释为多个潮汐尾观测。因此，我们可以排除潮汐冲击作为这种子结构的起源。最后，由调整后的条纹线参数可以证实，对于我们所研究的星团，逃逸主要发生在星团的潮汐半径上，公式为x_L =（GM/（Ω^2- \partial^2 Φ/ \partial R^2））^{1/3}。然而，我们发现，还有另一个极限半径，即“边缘”半径，它给出了恒星在围绕星系的一个星团轨道上可以逃逸的最小半径。对于偏心集群轨道的边缘半径缩小与轨道偏心率的增加（固定的偏心距离），但总是显着大于各自的近银河潮汐半径。事实上，我们研究的扩展和潮汐填充的星系团的边缘半径与它们的（拟合）King半径很好地吻合，这可能表明这两个量之间的基本联系。

英文摘要：

We investigate the epicyclic motion of stars escaping from star clusters. Using streaklines, we visualise the path of escaping stars and show how epicyclic motion leads to over- and underdensities in tidal tails of star clusters moving on circular and eccentric orbits about a galaxy. Additionally, we investigate the effect of the cluster mass on the tidal tails, by showing that their structure is better matched when the perturbing effect of the cluster mass is included. By adjusting streaklines to results of N-body computations we can accurately and quickly reproduce all observed substructure, especially the streaky features often found in simulations which may be interpreted in observations as multiple tidal tails. Hence, we can rule out tidal shocks as the origin of such substructures. Finally, from the adjusted streakline parameters we can verify that for the star clusters we studied escape mainly happens from the tidal radius of the cluster, given by x_L = (GM/(Ω^2-\partial^2Φ/\partial R^2))^{1/3}. We find, however, that there is another limiting radius, the "edge" radius, which gives the smallest radius from which a star can escape during one cluster orbit about the galaxy. For eccentric cluster orbits the edge radius shrinks with increasing orbital eccentricity (for fixed apocentric distance) but is always significantly larger than the respective perigalactic tidal radius. In fact, the edge radii of the clusters we investigated, which are extended and tidally filling, agree well with their (fitted) King radii, which may indicate a fundamental connection between these two quantities.

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摘要：

英文摘要：

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