Reionization of the Universe and the Early Production of Metals
Reionization of the Universe and the Early Production of Metals
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DOI：
10.1086/304548
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发表时间：
1996-12
期刊：
影响因子：
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通讯作者：
N. Gnedin;J. Ostriker
中科院分区：
文献类型：
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作者：
N. Gnedin;J. Ostriker
我们通过重新加热(在10≲z≲20时)和在z≈7时重新电离的连续阶段，相当详细地模拟了一个合理的宇宙学模型。我们假设在宇宙变得透明后，大质量恒星的形成效率适合离开宇宙，电离背景为J21≈0.4时(z=4)，接近(或略低于)观测值。由于同一颗恒星产生电离辐射和第一代重元素，因此在这一早期阶段产生了⟨Z/Z☉⟩~1/200的平均金属丰度，但这一平均值的变化很大，高密度区的Z/Z☉≈为1/30，低密度区(或NH Iα为1013.5 cm~2的Ly≲森林)基本上不含金属。当它发生时，再电离非常迅速(类似相变)，这将留下一个信号，可能会被非常大面积的米波无线电仪器探测到。此外，由于吸收边的存在，背景紫外辐射场将从1 Ryd急剧下降到4 Ryd，下降约10-3。模拟的体积太小，不足以形成L*星系，但模拟中发现的较小天体服从费伯-杰克逊关系。为了从理论上定量地探索“黑暗时代的终结”这一领域，数值模拟必须具有104.5 M☉量级的重子质量分辨率，具有高空间分辨率(≲1kpc)以解决强聚集，并允许详细和精确地处理辐射场和原子/分子物理。
We simulate a plausible cosmological model in considerable physical and numerical detail through the successive phases of reheating (at 10 ≲ z ≲ 20) and reionization at z ≈ 7. We assume an efficiency of high-mass star formation appropriate to leave the universe, after it becomes transparent, with an ionizing background J21 ≈ 0.4 (at z = 4), near (and perhaps slightly below) the observed value. Since the same stars produce the ionizing radiation and the first generation of heavy elements, a mean metallicity of ⟨Z/Z☉⟩ ~ 1/200 is produced in this early phase, but there is a large variation about this mean, with the high density regions having Z/Z☉ ≈ 1/30 and the low density regions (or the Lyα forest with NH I ≲ 1013.5 cm2) having essentially no metals. When it occurs, reionization is very rapid (phase change-like), which will leave a signature that may be detectable by very large area meter-wavelength radio instruments. Also, the background UV radiation field will show a sharp drop of ~10-3 from 1 to 4 ryd because of absorption edges. The simulated volume is too small to form L* galaxies, but the smaller objects that are found in the simulation obey the Faber-Jackson relation. In order to explore theoretically this domain of “the end of the dark ages” quantitatively, numerical simulations must have a mass resolution of the order of 104.5 M☉ in baryons, have high spatial resolution (≲1 kpc) to resolve strong clumping, and allow for detailed and accurate treatment of both the radiation field and atomic/molecular physics.