The Spatial Distribution of the Galactic First Stars. I. High-Resolution N-Body Approach
The Spatial Distribution of the Galactic First Stars. I. High-Resolution N-Body Approach
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银河系第一颗恒星的空间分布。
DOI：
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发表时间：
2006
期刊：
影响因子：
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通讯作者：
B. Gibson
中科院分区：
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作者：
E. Scannapieco;D. Kawata;C. Brook;R. Schneider;A. Ferrara;B. Gibson
我们研究了银河系无金属恒星的空间分布，结合一个极高分辨率（7.8 × 105 M每粒子）的冷暗物质N体模拟银河系的金属富集的半解析模型。这种方法使我们能够解析维里温度低至104K原子冷却极限的晕，并且尽管第一颗恒星的性质非常不确定，但它足够灵活，可以得出许多可靠的结论。银河系中无金属的恒星在一个很大的红移范围内形成，峰值在z = 10，但继续下降到z = 15，在很大的银心半径范围内形成恒星。只含有来自原始恒星的金属的恒星同样分布广泛。无论是将金属扩散效率改变2个数量级，还是大幅改变半解析模型中的近似值，都不会影响这些结果。因此，如果它们有足够长的寿命，那么在附近的银河系晕中应该会发现大量最初形成于原始星星团的恒星。对银河系晕星中金属丰度的观测应该被视为直接限制了原始恒星的性质，而今天缺乏无金属晕星应该被视为强烈暗示了原始初始质量函数的0.8 M的下限。
We study the spatial distribution of Galactic metal-free stars by combining an extremely high-resolution (7.8 × 105 M☉ per particle) cold dark matter N-body simulation of the Milky Way with a semianalytic model of metal enrichment. This approach allows us to resolve halos with virial temperatures down to the 104K atomic cooling limit, and it is sufficiently flexible to make a number of robust conclusions, despite the extremely uncertain properties of the first stars. Galactic metal-free stars are formed over a large redshift range, which peaks at z ≈ 10, but continues down to z ≈ 5, contributing stars at a wide range of Galactocentric radii. Stars containing only metals from primordial stars are similarly widespread. Neither changing the efficiency of metal dispersal by 2 orders of magnitude, nor drastically changing the approximations in our semianalytical model can affect these result. Thus, if they have sufficiently long lifetimes, a significant number of stars formed in initially primordial star clusters should be found in the nearby Galactic halo. Observations of metal abundances in Galactic halo stars should be taken as directly constraining the properties of primordial stars, and the lack of metal-free halo stars today should be taken as strongly suggesting a 0.8 M☉ lower limit on the primordial initial mass function.