Damped Lyman alpha systems and galaxy formation models – I. The radial distribution of cold gas at high z
Damped Lyman alpha systems and galaxy formation models – I. The radial distribution of cold gas at high z
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阻尼莱曼α系统和星系形成模型——I.高z处冷气体的径向分布
DOI：
10.1111/j.1365-2966.2001.04697.x
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发表时间：
2001
影响因子：
4.8
通讯作者：
J. Primack
中科院分区：
文献类型：
--
作者：
A. Maller;J. Prochaska;R. Somerville;J. Primack
我们在半解析模型中研究了阻尼Lyman α系统（DLAS）的性质，重点研究了该模型是否能再现Prochaska & Wolfe所描述的低电离金属谱线的运动学性质。在我们的模型中，我们探索了各种方法来模拟与星系相关的冷中性气体的径向分布，并发现我们的结果对这种成分非常敏感。如果我们使用基于Fall和Efstathiou工作的方法，其中盘的大小由角动量守恒决定，我们发现大多数DLAS对应于单个星系盘。这些模型一般不能再现观测到的速度宽度分布。在另一种模型中，气体盘相当广泛地延伸，DLAS的很大一部分来自于在一个共同光晕中相交的多个气体盘的视线。这些模型产生的运动学与观测数据吻合，似乎也与最近的流体动力学模拟结果吻合得很好。因此，我们得出结论，基于冷暗物质的星系形成模型可以与运动学数据相协调，但前提是要牺牲DLAS是由旋转支撑的气体盘产生的标准假设，其大小由角动量守恒决定。我们认为，高红移冷气体的分布可能是由另一个过程主导的，如合并引起的潮汐流。
We investigate the properties of damped Lyman α systems (DLAS) in semi-analytic models, focusing on whether the models can reproduce the kinematic properties of low-ionization metal lines described by Prochaska & Wolfe. We explore a variety of approaches for modelling the radial distribution of the cold neutral gas associated with the galaxies in our models, and find that our results are very sensitive to this ingredient. If we use an approach based on work by Fall & Efstathiou, in which the sizes of the discs are determined by conservation of angular momentum, we find that the majority of the DLAS correspond to a single galactic disc. These models generically fail to reproduce the observed distribution of velocity widths. In alternative models in which the gas discs are considerably more extended, a significant fraction of DLAS arise from lines of sight intersecting multiple gas discs in a common halo. These models produce kinematics that fit the observational data, and also seem to agree well with the results of recent hydrodynamical simulations. Thus we conclude that cold dark matter based models of galaxy formation can be reconciled with the kinematic data, but only at the expense of the standard assumption that DLAS are produced by rotationally supported gas discs whose sizes are determined by conservation of angular momentum. We suggest that the distribution of cold gas at high redshift may be dominated by another process, such as tidal streaming caused by mergers.