球状星团幼年期的超气泡动力学I。球状星团最初是如何失去冷气的？
Superbubble dynamics in globular cluster infancy I. How do globular clusters first lose their cold gas?
摘要：
球状星团早期演化的图像在最近几年已经被显著地修正了。目前的情况需要至少两代恒星，其中第一代（1G），因此也是原星团云，比目前占主导地位的第二代（2G）大得多。快速的气体排出被认为是解开大多数1G恒星的束缚。气体排出也是强制性的，以去除富含金属的超新星喷出物，这在2G恒星中没有发现。长期以来，人们一直认为超新星本身是气体排出的媒介，这是基于粗略的能量论论点。在这里，我们假设气体的驱逐发生通过形成一个超级气泡，并描述了薄壳模型的运动学。我们发现超新星驱动的壳层在达到逃逸速度之前就被瑞利-泰勒不稳定性破坏了，除了质量最小和最大的星团。需要更多的能量来驱逐气体，这可能是由恒星残余物上的相干吸积开始提供的。如果一个球状星团恰好形成在这样一个射电瓣的前面，那么用计划中的平方公里阵列射电望远镜对着极化的背景射电瓣，在法拉第旋转图中就可以观察到这样的kpc大小的气泡。
英文摘要：
The picture of the early evolution of globular clusters has been significantly revised in recent years. Current scenarios require at least two generations of stars of which the first generation (1G), and therefore also the protocluster cloud, has been much more massive than the currently predominating second generation (2G). Fast gas expulsion is thought to unbind the majority of the 1G stars. Gas expulsion is also mandatory to remove metal-enriched supernova ejecta, which are not found in the 2G stars. It has long been thought that the supernovae themselves are the agent of the gas expulsion, based on crude energetics arguments. Here, we assume that gas expulsion happens via the formation of a superbubble, and describe the kinematics by a thin-shell model. We find that supernova- driven shells are destroyed by the Rayleigh-Taylor instability before they reach escape speed for all but perhaps the least massive and most extended clusters. More power is required to expel the gas, which might plausibly be provided by a coherent onset of accretion onto the stellar remnants. The resulting kpc-sized bubbles might be observable in Faraday rotation maps with the planned Square Kilometre Array radio telescope against polarised background radio lobes if a globular cluster would happen to form in front of such a radio lobe.
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