标题： 一些星系盘的稳定性仍然令人困惑 显示英文标题

标题： The stability of some galaxy disks is still perplexing

摘要： 一些盘星系如何避免形成棒状结构的问题仍未得到解决。 许多具有合理性质的星系模型仍然表现出强烈的不稳定性，这些不稳定性会迅速形成强棒结构，但尚未提出广泛接受的观点来解释某些盘星系是如何避免这种不稳定的。 令人鼓舞的是，并非所有在最近的宇宙学模拟中形成的星系都拥有棒状结构，但这一结果的动态解释尚不清楚。 形成棒状结构的不稳定模式被理解为一种驻波，在一个腔体中传播，该腔体在盘星系中心和共转半径处反射，且在共转半径处有放大效应。 在这里，我们使用模拟来探讨另一种可能抑制反馈回路并因此有助于稳定的想法，即让盘星系中心变得动力学上热化和/或减少内盘的质量，这可能是被凸起所掩盖的。 不幸的是，我们发现这两种策略对我们尝试过的模型中盘的总体稳定性并没有太大影响。 虽然深度密度削减确实可以通过中心阻止反馈，但它们仍然会反射入射波，从而引发一种略有不同的不稳定性，这再次导致形成强棒结构。 显示英文摘要

摘要： The problem of how some disk galaxies avoid forming bars remains unsolved. Many galaxy models having reasonable properties continue to manifest vigorous instabilities that rapidly form strong bars and no widely-accepted idea has yet been advanced to account for how some disk galaxies manage to avoid this instability. It is encouraging that not all galaxies formed in recent cosmological simulations possess bars, but the dynamical explanation for this result is unclear. The unstable mode that creates a bar is understood as a standing wave in a cavity that reflects off the disk center and the corotation radius, with amplification at corotation. Here we use simulations to address one further idea that may perhaps inhibit the feedback loop and therefore contribute to stability, which is to make the disk center dynamically hot and/or to taper away mass from the inner disk, which could be masked by a bulge. Unfortunately, we find that neither strategy makes much difference to the global stability of the disk in the models we have tried. While deep density cutouts do indeed prevent feedback through the center, they still reflect incoming waves and thereby provoke a slightly different instability that again leads to a strong bar.