On the evolution of the H i column density distribution in cosmological simulations
On the evolution of the H i column density distribution in cosmological simulations
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DOI：
10.1093/mnras/stt066
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发表时间：
2012-10
影响因子：
4.8
通讯作者：
A. Rahmati;A. Pawlik;Milan Raivcevi'c;J. Schaye
中科院分区：
文献类型：
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作者：
A. Rahmati;A. Pawlik;Milan Raivcevi'c;J. Schaye
我们使用一组宇宙学模拟结合辐射传递计算来研究中性氢在再电离后宇宙中的分布。我们评估了元星系电离背景辐射、碰撞电离辐射和弥散复合辐射对红移z = 0.5时总电离率的贡献。我们发现，在氢自屏蔽变得重要的密度以上，与解析计算和以前的工作是一致的。然而，由于弥漫性复合辐射，其强度峰值在相同的密度，高电离区和自屏蔽区之间的过渡比通常假设的更平滑。我们提供了模拟光电离速率作为密度函数的拟合函数，并表明使用拟合速率的后处理模拟产生的结果与原始辐射传输计算非常吻合。预测的中性氢柱密度分布与观测结果吻合得很好。特别是，模拟重现了Lyman极限和弱阻尼Lyα体系在z = 3以下的柱密度分布明显缺乏演化。随着红移的减小，碰撞电离的重要性增加，影响了低柱密度端的演化。另一方面，模拟预测强阻尼Lyα系统的丰度，以大致跟踪宇宙恒星形成速率密度。
We use a set of cosmological simulations combined with radiative transfer calculations to investigate the distribution of neutral hydrogen in the post-reionization Universe. We assess the contributions from the metagalactic ionizing background, collisional ionization and diffuse recombination radiation to the total ionization rate at redshifts z = 0 5. We find that the densities above which hydrogen self-shielding becomes important are consistent with analytic calculations and previous work. However, because of diffuse recombination radiation, whose intensity peaks at the same density, the transition between highly ionized and self-shielded regions is smoother than what is usually assumed. We provide fitting functions to the simulated photoionization rate as a function of density and show that post-processing simulations with the fitted rates yields results that are in excellent agreement with the original radiative transfer calculations. The predicted neutral hydrogen column density distributions agree very well with the observations. In particular, the simulations reproduce the remarkable lack of evolution in the column density distribution of Lyman limit and weak damped Lyα systems below z = 3. The evolution of the low column density end is affected by the increasing importance of collisional ionization with decreasing redshift. On the other hand, the simulations predict the abundance of strong damped Lyα systems to broadly track the cosmic star formation rate density.