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arXiv 2008.05663astro-ph.GAastro-ph.CO
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流动速度和莱曼-沃纳辐射对第一批恒星形成的影响

The influence of streaming velocities and Lyman-Werner radiation on the formation of the first stars

Anna T. P. Schauer, Simon C. O. Glover, Ralf S. Klessen, Paul Clark

备注：
15 pages, 12+1 figures, 2 fit-formulas, accepted by MNRAS
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摘要：

宇宙中的第一批恒星，即所谓的第三星族恒星，形成于维里温度为$T_{\rm vir} < 10^{4}$ ~K的小型暗物质迷你晕中。这些微晕中的冷却主要由分子氢（H $_{2}$）控制，因此只有在那些形成足够H $_{2}$的微晕中才有可能形成星族III的恒星，从而在短时间内冷却。由于H $_{2}$冷却在质量更大的迷你晕中更有效，因此存在一个临界晕质量尺度$M_{\rm min}$，高于该尺度，第三星族恒星的形成才成为可能。两个重要的过程可以改变这个最小质量尺度：重子相对于暗物质的流动和H $_{2}$在高红移的莱曼-维尔纳（LW）背景下的光解离。在本文中，我们提出了一套高分辨率的宇宙学模拟，研究这些过程的影响，对$M_{\rm min}$和$M_{\rm ave}$（恒星形成的平均微晕质量），无论是单独和组合。我们发现，流有一个更大的影响$M_{\rm min}$比LW的背景，但也有两种效果是加性的。我们还提供了拟合函数量化的依赖$M_{\rm ave}$和$M_{\rm min}$上的流速度和强度的LW背景。

英文摘要：

The first stars in the Universe, the so-called Population III stars, form in small dark matter minihaloes with virial temperatures $T_{\rm vir} < 10^{4}$~K. Cooling in these minihaloes is dominated by molecular hydrogen (H$_{2}$), and so Population III star formation is only possible in those minihaloes that form enough H$_{2}$ to cool on a short timescale. As H$_{2}$ cooling is more effective in more massive minihaloes, there is therefore a critical halo mass scale $M_{\rm min}$ above which Population III star formation first becomes possible. Two important processes can alter this minimum mass scale: streaming of baryons relative to the dark matter and the photodissociation of H$_{2}$ by a high redshift Lyman-Werner (LW) background. In this paper, we present results from a set of high resolution cosmological simulations that examine the impact of these processes on $M_{\rm min}$ and on $M_{\rm ave}$ (the average minihalo mass for star formation), both individually and in combination. We show that streaming has a bigger impact on $M_{\rm min}$ than the LW background, but also that both effects are additive. We also provide fitting functions quantifying the dependence of $M_{\rm ave}$ and $M_{\rm min}$ on the streaming velocity and the strength of the LW background.

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