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arXiv 1003.0472astro-ph.CO
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第一个星系：化学富集，混合和恒星形成

The First Galaxies: Chemical Enrichment, Mixing, and Star Formation

Thomas H. Greif, Simon C. O. Glover, Volker Bromm, Ralf S. Klessen

备注：
13 pages, 9 figures, published in ApJ
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摘要：

利用三维宇宙学模拟，我们研究了第一个星系之一的组装过程，该星系总质量为10^8 M_sun，在z = 10处坍缩。我们的主要目标是跟踪运输的重化学元素产生和分散的对不稳定超新星爆炸的一个minihalo的祖先。在这种程度上，我们将一个有效的算法到我们的光滑粒子流体动力学代码，近似模型湍流混合扩散过程。我们研究了这种混合，没有辐射反馈的人口III恒星，随后形成在邻近的minihalos。我们的模拟使我们能够约束第二代恒星形成的初始条件，在第一个星系本身，以及超新星爆炸后维里化的迷你晕内部。我们发现，大多数迷你晕仍然不受电离辐射或超新星遗迹的影响，而有些则被大量光热加热并富集到超临界水平，可能导致低质量的第三族甚至第二族恒星的形成。在新形成的星系中心，10 ^5 M太阳的冷而致密的气体均匀地富集到10^-3 Z太阳，处于坍缩状态，这表明一个星族II恒星的星团将形成。詹姆斯·韦伯太空望远镜可能探测到的第一批星系，因此已经包含了从较低红移中所熟悉的恒星星族。

英文摘要：

Using three-dimensional cosmological simulations, we study the assembly process of one of the first galaxies, with a total mass of 10^8 M_sun, collapsing at z = 10. Our main goal is to trace the transport of the heavy chemical elements produced and dispersed by a pair-instability supernova exploding in one of the minihalo progenitors. To this extent, we incorporate an efficient algorithm into our smoothed particle hydrodynamics code which approximately models turbulent mixing as a diffusion process. We study this mixing with and without the radiative feedback from Population III stars that subsequently form in neighboring minihalos. Our simulations allow us to constrain the initial conditions for second-generation star formation, within the first galaxy itself, and inside of minihalos that virialize after the supernova explosion. We find that most minihalos remain unscathed by ionizing radiation or the supernova remnant, while some are substantially photoheated and enriched to supercritical levels, likely resulting in the formation of low-mass Population III or even Population II stars. At the center of the newly formed galaxy, 10^5 M_sun of cold, dense gas uniformly enriched to 10^-3 Z_sun are in a state of collapse, suggesting that a cluster of Population II stars will form. The first galaxies, as may be detected by the James Webb Space Telescope, would therefore already contain stellar populations familiar from lower redshifts.

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