FEEDBACK FROM MASSIVE STARS AND GAS EXPULSION FROM PROTO-GLOBULAR CLUSTERS

FEEDBACK FROM MASSIVE STARS AND GAS EXPULSION FROM PROTO-GLOBULAR CLUSTERS
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来自大质量恒星的反馈和原球状星团的气体排出

DOI：
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发表时间：
2015
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影响因子：
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通讯作者：
A. D'ercole
A. D'ercole
中科院分区：
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文献类型：
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作者：
F. Calura;C. G. Few;D. Romano;A. D'ercole

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球状星团(GC)的结构比之前认为的要复杂得多，至少有两代恒星，呈现出明显不同的化学丰度。解释GC中丰度模式的情景大多假设最初的星团必须比今天大得多，第二代恒星起源于第一代恒星(FG)排放的气体。大多数GC中缺乏金属丰度扩散，这进一步要求FG喷出的富含超新星的气体在∼30Myr内完全消失，这一假说从未通过三维流体动力学模拟进行验证。在本文中，我们使用包括来自风和超新星的恒星反馈、辐射冷却和自引力的3D流体动力学模拟来研究初始质量为MTOT∼107M⊙的大质量原GC中OB缔合的真实分布是否足以驱逐其全部气体含量。我们的数值实验表明，不同缔合的连贯性起着基本的作用：当气泡相互作用、扭曲和合并时，它们会挖出狭窄的隧道，越来越深地延伸到星系团的最内部区域，气体能够通过这些隧道逃逸。我们的结果表明，在3Myr之后，来自恒星风的反馈可以去除40%的原始气体，而在14Myr之后，初始气体质量的99%已经被去除。
Globular clusters (GCs) are considerably more complex structures than previously thought, harboring at least two stellar generations that present clearly distinct chemical abundances. Scenarios explaining the abundance patterns in GCs mostly assume that originally the clusters had to be much more massive than today, and that the second generation of stars originates from the gas shed by stars of the first generation (FG). The lack of metallicity spread in most GCs further requires that the supernova-enriched gas ejected by the FG is completely lost within ∼30 Myr, a hypothesis never tested by means of three-dimensional hydrodynamic simulations. In this paper, we use 3D hydrodynamic simulations including stellar feedback from winds and supernovae, radiative cooling and self-gravity to study whether a realistic distribution of OB associations in a massive proto-GC of initial mass Mtot ∼ 107 M⊙ is sufficient to expel its entire gas content. Our numerical experiment shows that the coherence of different associations plays a fundamental role: as the bubbles interact, distort, and merge, they carve narrow tunnels that reach deeper and deeper toward the innermost cluster regions, and through which the gas is able to escape. Our results indicate that after 3 Myr, the feedback from stellar winds is responsible for the removal of ∼40% of the pristine gas, and that after 14 Myr, 99% of the initial gas mass has been removed.