解决绕天炉座矮星系运行的球状星团的时间问题
Resolving the timing problem of the globular clusters orbiting the Fornax dwarf galaxy
摘要：
我们重新调查的生存的五个球状星团围绕天炉座矮星系在标准和修改后的牛顿动力学的老问题。对于第一次在历史上的主题，我们使用精确的质量模型的天炉座矮，通过牛仔裤建模最近发表的视线速度色散数据，我们也不辞职圆形轨道的球状星团。以前设想的问题源于将球状星团的起始距离固定为小于潮汐半径的一半。我们放松了这个限制，因为绝对没有证据证明它，并表明暗物质的范例，无论是尖或核心暗物质配置文件，没有麻烦维持两个最小的质量球状星团的轨道哈勃时间几乎无论其初始距离天炉座。三个最大的球状星团可以留在轨道上，只要它们的起始距离稍微在潮汐半径之外。修正后的牛顿动力学的前景也不像以前报道的那样暗淡。虽然在MOND中潮汐半径内的动力学摩擦要强得多，但由于没有恒星，外部的动力学摩擦可以忽略不计。这使得高径向轨道得以生存，但更重要的是，距离超过天炉座潮汐半径85%的圆形轨道可以无限期地生存。讨论了球状星团在这个距离上的圆轨道上的概率，并与它们目前的投影距离进行了比较。最后，如果我们忽略最大质量的球状星团的存在（给它一个大的视线距离），我们证明了剩下的四个球状星团可以在哈勃时间的潮汐半径内生存，具有完美的合理轨道。
英文摘要：
We re-investigate the old problem of the survival of the five globular clusters orbiting the Fornax dwarf galaxy in both standard and modified Newtonian dynamics. For the first time in the history of the topic, we use accurate mass models for the Fornax dwarf, obtained through Jeans modelling of the recently published line of sight velocity dispersion data, and we are also not resigned to circular orbits for the globular clusters. Previously conceived problems stem from fixing the starting distances of the globulars to be less than half the tidal radius. We relax this constraint since there is absolutely no evidence for it and show that the dark matter paradigm, with either cusped or cored dark matter profiles, has no trouble sustaining the orbits of the two least massive globular clusters for a Hubble time almost regardless of their initial distance from Fornax. The three most massive globulars can remain in orbit as long as their starting distances are marginally outside the tidal radius. The outlook for modified Newtonian dynamics is also not nearly as bleak as previously reported. Although dynamical friction inside the tidal radius is far stronger in MOND, outside dynamical friction is negligible due to the absence of stars. This allows highly radial orbits to survive, but more importantly circular orbits at distances more than 85% of Fornax's tidal radius to survive indefinitely. The probability of the globular clusters being on circular orbits at this distance compared with their current projected distances is discussed and shown to be plausible. Finally, if we ignore the presence of the most massive globular (giving it a large line of sight distance) we demonstrate that the remaining four globulars can survive within the tidal radius for the Hubble time with perfectly sensible orbits.
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