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arXiv 2303.04572astro-ph.GA
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基于低红移莱曼连续谱巡天和$z>8$恒星形成星系推断的再电离历史经验模型

An Empirical reionization history model inferred from the low-redshift Lyman continuum survey and the star-forming galaxies at $z>8$

Yu-Heng Lin, Claudia Scarlata, Hayley Williams, Wenlei Chen, Patrick Kelly, Danial Langeroodi, Jens Hjorth, John Chisholm, Anton M. Koekemoer, Adi Zitrin, Jose M. Diego

备注：
10 pages, 7 figures, accepted by MNRAS
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AI总结：

本文通过分析z>8星系样本，构建逻辑回归和经验模型，发现中等紫外光度星系逃逸分数较大，暗星系贡献主要电离光子，亮星系贡献最小。

摘要：

我们对RX J2129.4+0009引力透镜星系团背后发现的三个$z>8$星系样本的静止系紫外和光学光谱进行了新的分析。我们将这些观测与文献中具有类似测量的$z>7.5$星系相结合。正如其他研究已指出的，高[\oiii]$\lambda$5007/[\oii]$\lambda$3727比值（$O_{32}$）和陡峭的紫外连续谱斜率（$\beta$）与低红移莱曼连续谱发射体观测到的值一致，表明此类星系对星系间介质的电离预算有所贡献。我们构建了一个逻辑回归模型，基于测量的\MUV、$\beta$和$O_{32}$来估计星系成为莱曼连续谱发射体的概率。利用该概率和紫外光度函数，我们构建了一个经验模型来估计高红移星系对再电离的贡献。我们分析中的首选情景表明，在$z\sim8$时，星系群体的平均逃逸分数（即包括莱曼连续谱发射体和非发射体）随\MUV变化，中等紫外光度（$-19<M_{UV}<-16$）的星系具有较大的逃逸分数。紫外光度较暗的星系（$-16<M_{UV}<-13.5$）贡献了大部分电离光子。暗星系与亮星系的相对贡献取决于红移，中等紫外星系随时间推移变得更加重要。紫外亮星系虽然在给定的log($O_{32}$)和$\beta$下更可能是莱曼连续谱发射体，但对总电离光子预算的贡献最小。

英文摘要：

We present a new analysis of the rest-frame UV and optical spectra of a sample of three $z>8$ galaxies discovered behind the gravitational lensing cluster RX\,J2129.4+0009. We combine these observations with $z>7.5$ galaxies from the literature, for which similar measurements are available. As already pointed out in other studies, the high [\oiii]$λ$5007/[\oii]$λ$3727 ratios ($O_{32}$) and steep UV continuum slopes ($β$) are consistent with the values observed for low redshift Lyman continuum emitters, suggesting that such galaxies contribute to the ionizing budget of the intergalactic medium. We construct a logistic regression model to estimate the probability of a galaxy being a Lyman continuum emitter based on the measured \MUV, $β$, and $O_{32}$. Using this probability and the UV luminosity function, we construct an empirical model that estimates the contribution of high redshift galaxies to reionization. The preferred scenario in our analysis shows that at $z\sim8$, the average escape fraction of the galaxy population (i.e., including both LyC emitters and non-emitters) varies with \MUV, with intermediate UV luminosity ($-19<M_{UV}<-16$) galaxies having larger escape fraction. Galaxies with faint UV luminosity ($-16<M_{UV}<-13.5$) contribute most of the ionizing photons. The relative contribution of faint versus bright galaxies depends on redshift, with the intermediate UV galaxies becoming more important over time. UV bright galaxies, although more likely to be LCEs at a given log($O_{32}$) and $β$, contribute the least of the total ionizing photon budget.

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