Cosmic evolution of the atomic and molecular gas contents of galaxies
Cosmic evolution of the atomic and molecular gas contents of galaxies
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DOI：
10.1111/j.1365-2966.2011.19583.x
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发表时间：
2011-05
影响因子：
4.8
通讯作者：
C. Lagos;C. Baugh;C. Lacey;A. Benson;H. Kim;Chris Power Icc;Durham;Caltech;Melbourne.;W. University
中科院分区：
文献类型：
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作者：
C. Lagos;C. Baugh;C. Lacey;A. Benson;H. Kim;Chris Power Icc;Durham;Caltech;Melbourne.;W. University
我们使用Λ冷暗物质框架下的星系形成模型galform，通过将星际介质分解为其原子和分子氢组分来研究星系冷气体含量的演化。我们使用Blitz & Rosolowsky的基于压力的经验关系和Krumholz， McKeee & Tumlinson的理论模型两种不同的方法计算了每个星系中分子与原子的氢质量比H_(2)/H i，并将它们应用于一致计算星系的恒星形成率。我们发现基于Blitz & Rosolowsky定律的模型预测了一个H质量函数，^(12)CO（1-0）光度函数，H_(2)/H i与恒星和冷气体质量的相关性，以及红外- ^(12)CO分子光度关系，与局部和高红移观测结果很好地吻合。H - i质量函数随红移的演化较弱，高质量星系的数量密度随红移的增加而减小。在H_2质量函数中，大质量星系的数量密度在z= 0 ~ 2时呈强增长，在z= 4前呈弱演化。我们还发现，星系的H_(2)/H i与恒星和冷气体质量以及红移密切相关。H_(2)/H i与恒星和冷气体质量之间的相关性斜率几乎没有变化，但从z= 0到8，归一化程度增加了两个数量级。H_2质量函数和H_(2)/H i的强烈演化主要是由于星系大小的演化，其次是气体组分的演化。预测的宇宙密度演化与从阻尼Lyα系统推断的观测演化一致，并且总是由低质量和中质量晕的H含量主导。我们发现，由于分辨率有限，以往的理论研究在很大程度上高估了全球H_(2)/H i的红移演化。我们预测在z≈3.5处ρH_2/ρH i≈1.2的最大值。
We study the evolution of the cold gas content of galaxies by splitting the interstellar medium into its atomic and molecular hydrogen components, using the galaxy formation model galform in the Λ cold dark matter framework. We calculate the molecular-to-atomic hydrogen mass ratio, H_(2)/H i, in each galaxy using two different approaches, the pressure-based empirical relation of Blitz & Rosolowsky and the theoretical model of Krumholz, McKeee & Tumlinson, and apply them to consistently calculate the star formation rates of galaxies. We find that the model based on the Blitz & Rosolowsky law predicts an H i mass function, ^(12)CO (1–0) luminosity function, correlations between H_(2)/H i and stellar and cold gas mass, and infrared–^(12)CO molecule luminosity relation in good agreement with local and high-redshift observations. The H i mass function evolves weakly with redshift, with the number density of high-mass galaxies decreasing with increasing redshift. In the case of the H_2 mass function, the number density of massive galaxies increases strongly from z= 0 to 2, followed by weak evolution up to z= 4. We also find that H_(2)/H i of galaxies is strongly dependent on stellar and cold gas mass, and also on redshift. The slopes of the correlations between H_(2)/H i and stellar and cold gas mass hardly evolve, but the normalization increases by up to two orders of magnitude from z= 0 to 8. The strong evolution in the H_2 mass function and H_(2)/H i is primarily due to the evolution in the sizes of galaxies and, secondarily, in the gas fractions. The predicted cosmic density evolution of H i agrees with the observed evolution inferred from damped Lyα systems, and is always dominated by the H i content of low- and intermediate-mass haloes. We find that previous theoretical studies have largely overestimated the redshift evolution of the global H_(2)/H i due to limited resolution. We predict a maximum of ρH_2/ρH i ≈ 1.2 at z≈ 3.5.