Metal-enriched galaxies in the first ∼1 billion years: evidence of a smooth metallicity evolution at z ∼ 5
Metal-enriched galaxies in the first ∼1 billion years: evidence of a smooth metallicity evolution at z ∼ 5
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DOI：
10.1093/mnras/stz3000
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发表时间：
2019-10
影响因子：
4.8
通讯作者：
Suraj Poudel;V. Kulkarni;Frances H. Cashman;B. Frye;C. Péroux;H. Rahmani;S. Quiret
中科院分区：
文献类型：
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作者：
Suraj Poudel;V. Kulkarni;Frances H. Cashman;B. Frye;C. Péroux;H. Rahmani;S. Quiret
我们提出了7个新的丰度测量的元素O，C和Si在z > 4.5，增加了一倍，现有的样品中的弱贫化元素在气体丰富的星系，以约束宇宙金属演化的第一个100亿年。这些测量是基于类星体的阻尼莱曼α吸收体（DLAs）和亚DLAs的光谱，这些光谱是由麦哲伦南望远镜上的麦哲伦稻盛京瓷Echelle（MIKE）和麦哲伦Echellette（法师）摄谱仪以及甚大望远镜上的X-Shooter摄谱仪获得的。我们联合收割机将这些新的测量结果与文献中的测量结果结合起来，估计z = 4.8时$N_{\rm H\，{\small I}}$加权分组平均金属丰度为-1.51 ± 0.18。这个金属丰度值与低红移DLAs的预测非常一致，支持了金属丰度在z = 1.5时平滑演化的解释，而不是在z > 4.7时突然下降。此外，在我们的不确定性范围内，DLAs和子DLAs的金属丰度演化趋势相似。我们还发现，[C/O]比为z105的DLAs是一致的，非常贫金属的DLAs。此外，使用[C/O]和[Si/O]来约束核合成模型，我们估计，三个相对贫金属的DLA的祖星星质量的概率分布集中在12-17 M质量。最后，z 5吸收体显示出与较低红移的DLAs不同的金属性-速度色散关系，这表明它们可能正在追踪不同的星系群。
We present seven new abundance measurements of the elements O, C, and Si at z > 4.5, doubling the existing sample of weakly depleted elements in gas-rich galaxies, in order to constrain the first ∼1 billion years of cosmic metal evolution. These measurements are based on quasar spectra of damped Lyman α absorbers (DLAs) and sub-DLAs obtained with the Magellan Inamori Kyocera Echelle (MIKE) and Magellan Echellette (MagE) spectrographs on Magellan-South, and the X-Shooter spectrograph on the Very Large Telescope. We combine these new measurements with those drawn from the literature to estimate the $N_{\rm H\, {\small I}}$-weighted binned mean metallicity of −1.51 ± 0.18 at z = 4.8. This metallicity value is in excellent agreement with the prediction from lower redshift DLAs, supporting the interpretation that the metallicity evolution is smooth at z ∼ 5, rather than showing a sudden decline at z > 4.7. Furthermore, the metallicity evolution trends for the DLAs and sub-DLAs are similar within our uncertainties. We also find that the [C/O] ratios for z ∼ 5 DLAs are consistent with those of the very metal-poor DLAs. Additionally, using [C/O] and [Si/O] to constrain the nucleosynthesis models, we estimate that the probability distributions of the progenitor star masses for three relatively metal-poor DLAs are centred around 12–17 M⊙. Finally, the z ∼ 5 absorbers show a different metallicity–velocity dispersion relation than lower redshift DLAs, suggesting that they may be tracing a different population of galaxies.