The first generation of stars in the Λ cold dark matter cosmology
The first generation of stars in the Λ cold dark matter cosmology
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DOI：
10.1111/j.1365-2966.2007.11814.x
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发表时间：
2006-10
影响因子：
4.8
通讯作者：
Liang Gao;N. Yoshida;Tom Abel;C. Frenk;A. Jenkins;V. Springel
中科院分区：
文献类型：
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作者：
Liang Gao;N. Yoshida;Tom Abel;C. Frenk;A. Jenkins;V. Springel
我们使用光滑粒子流体动力学(SPH)进行了大量高分辨率的宇宙学模拟，研究了{Lambda}CDM宇宙学中第一个发光物体的形成。我们跟踪了八个早期结构中原始气体云的崩溃，并记录了第一批恒星形成云的散布。我们的第一批天体跨越了从z{约x}10到z{约x}50的编队红移，覆盖了一个数量级的晕质量。我们发现，中心恒星形成云的物理性质在所有模拟的天体中都非常相似，尽管在形成、红移和环境方面有很大的不同。这表明，第一批恒星的形成路径在很大程度上与坍塌红移无关；云的物理性质与主晕的自旋、质量或组装历史几乎没有相关性。红移较大的原恒星天体由于密度较高而崩塌的速度更快，这加速了分子氢的形成，增强了初始冷却，缩短了动力学时间尺度。恒星形成云的质量覆盖范围很广，从几百个太阳质量到几千个太阳质量不等，并呈现出各种形态：一些具有几乎被旋转支撑的盘状结构；一些形成扁平的椭球体；还有一些形成棒状。它们都形成了单一的原恒星“种子”，直到中心气体变得非常厚到H{sub2}冷却线的那一刻，它才会分裂成多个物体。此时，到达中心的瞬时质量吸积率因物体而异，其中盘状结构具有最小的质量吸积率。恒星形成云的形成年代和性质对宇宙学参数的取值很敏感。
We have performed a large set of high-resolution cosmological simulations using smoothed particle hydrodynamics (SPH) to study the formation of the first luminous objects in the {Lambda}CDM cosmology. We follow the collapse of primordial gas clouds in eight early structures and document the scatter in the properties of the first star-forming clouds. Our first objects span formation redshifts from z {approx} 10 to z {approx} 50 and cover an order of magnitude in halo mass. We find that the physical properties of the central star-forming clouds are very similar in all of the simulated objects despite significant differences in formation redshift and environment. This suggests that the formation path of the first stars is largely independent of the collapse redshift; the physical properties of the clouds have little correlation with spin, mass, or assembly history of the host halo. The collapse of proto-stellar objects at higher redshifts progresses much more rapidly due to the higher densities, which accelerates the formation of molecular hydrogen, enhances initial cooling and shortens the dynamical timescales. The mass of the star-forming clouds cover a broad range, from a few hundred to a few thousand solar masses, and exhibit various morphologies: some have disk-like structures which are nearly rotational supported; others form flattened spheroids; still others form bars. All of them develop a single protostellar ''seed'' which does not fragment into multiple objects up to the moment that the central gas becomes optically thick to H{sub 2} cooling lines. At this time, the instantaneous mass accretion rate onto the centre varies significantly from object to object, with disk-like structures having the smallest mass accretion rates. The formation epoch and properties of the star-forming clouds are sensitive to the values of cosmological parameters.