The Mass–Metallicity Relation at z ≃ 8: Direct-method Metallicity Constraints and Near-future Prospects
The Mass–Metallicity Relation at z ≃ 8: Direct-method Metallicity Constraints and Near-future Prospects
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DOI：
10.3847/1538-4357/abb943
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发表时间：
2020-06
期刊：
影响因子：
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通讯作者：
T. Jones;R. Sanders;G. Roberts-Borsani;R. Ellis;N. Laporte;T. Treu;Y. Harikane
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文献类型：
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作者：
T. Jones;R. Sanders;G. Roberts-Borsani;R. Ellis;N. Laporte;T. Treu;Y. Harikane
z bbb70星系的物理性质对理解恒星形成的早期阶段和宇宙再电离过程都很有意义。化学丰度测量提供了关于整体恒星形成历史的有价值的信息，因此电离光子的产生，以及在如此高的红移下预期的快速气体吸积。我们使用已报道的[O iii] 88 μm发射和恒星形成速率的测量值，使用直接法估计了z = 7.1-9.1的五个星系的气相氧丰度。我们发现在固定恒星质量下，典型的氧丰度= 7.9（~ 0.2倍太阳值），从z≃8到0的演化指数为0.9±0.5。这些结果与理论预测一致，尽管在质量和金属丰度方面存在较大的（保守的）不确定性。我们评估了统计和系统的不确定性，以确定阿塔卡马大型毫米/亚毫米阵列（ALMA）和詹姆斯韦伯太空望远镜（JWST）有希望的改进方法。我们特别强调[O iii] 52 μm是稳健金属丰度测量的一个有价值的特征。对于z≈5 ~ 8的星系，将[O iii] 52 μm与静框光学强谱结合，可以合理地获得0.1 ~ 0.2个指数的O/H丰度精度。它还可以通过千秒差距尺度上的可分辨丰度来探测气体混合和合并。利用ALMA和JWST，直接测量金属丰度将在再电离时代变得非常容易。
Physical properties of galaxies at z > 7 are of interest for understanding both the early phases of star formation and the process of cosmic reionization. Chemical abundance measurements offer valuable information on the integrated star formation history, and hence ionizing photon production, as well as the rapid gas accretion expected at such high redshifts. We use reported measurements of [O iii] 88 μm emission and star formation rate to estimate gas-phase oxygen abundances in five galaxies at z = 7.1–9.1 using the direct method. We find typical abundances = 7.9 (∼0.2 times the solar value) and an evolution of 0.9 ± 0.5 dex in oxygen abundance at fixed stellar mass from z ≃ 8 to 0. These results are compatible with theoretical predictions, albeit with large (conservative) uncertainties in both mass and metallicity. We assess both statistical and systematic uncertainties to identify promising means of improvement with the Atacama Large Millimeter/submillimeter Array (ALMA) and the James Webb Space Telescope (JWST). In particular we highlight [O iii] 52 μm as a valuable feature for robust metallicity measurements. Precision of 0.1–0.2 dex in -based O/H abundance can be reasonably achieved for galaxies at z ≈ 5–8 by combining [O iii] 52 μm with rest-frame optical strong lines. It will also be possible to probe gas mixing and mergers via resolved -based abundances on kiloparsec scales. With ALMA and JWST, direct metallicity measurements will thus be remarkably accessible in the reionization epoch.