Properties of the Lowest-metallicity Galaxies over the Redshift Range z = 0.2 to z = 1
Properties of the Lowest-metallicity Galaxies over the Redshift Range z = 0.2 to z = 1
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DOI：
10.3847/1538-4357/ac81c7
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发表时间：
2022-07
期刊：
影响因子：
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通讯作者：
I. Laseter;A. Barger;L. Cowie;A. Taylor
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作者：
I. Laseter;A. Barger;L. Cowie;A. Taylor
低金属丰度星系可能为了解星系的进化史提供关键的见解。具有强发射谱线和高等效宽度（静止框架EW(Hβ)≥30 Å）的星系是z ~ 1金属丰度最低的星系的理想候选者。利用Keck/DEIMOS光谱数据库，在z = 0.2和z = 1之间的大约18000个星系中，我们寻找这种极端发射线星系，目的是确定它们的金属丰度。使用强大的直接T - e方法，我们确定了8个新的极端金属贫星系（xmpg），它们的12+log O/H≤7.65，其中一个为6.949±0.091，使其成为迄今为止在这些红移中报道的金属丰度最低的星系。我们还改进了以前工作中另外两个xmpg的金属丰度。我们使用瞬时星暴模型和连续星暴模型研究了Hβ的演化，发现xmpg最适合连续星暴模型。最后，研究了金属堆积物和发射线强度与年龄的关系。
Low-metallicity galaxies may provide key insights into the evolutionary history of galaxies. Galaxies with strong emission lines and high equivalent widths (rest-frame EW(Hβ) ≳ 30 Å) are ideal candidates for the lowest-metallicity galaxies to z ∼ 1. Using a Keck/DEIMOS spectral database of about 18,000 galaxies between z = 0.2 and z = 1, we search for such extreme emission-line galaxies with the goal of determining their metallicities. Using the robust direct T e method, we identify eight new extremely metal-poor galaxies (XMPGs) with 12+log O/H ≤7.65, including one at 6.949 ± 0.091, making it the lowest-metallicity galaxy reported to date at these redshifts. We also improve upon the metallicities for two other XMPGs from previous work. We investigate the evolution of Hβ using both instantaneous and continuous starburst models, finding that XMPGs are best characterized by continuous starburst models. Finally, we study the dependence on age of the buildup of metals and the emission-line strength.