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arXiv 1503.00320astro-ph.GA
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具有最高[ OIII ]/[ OII ]比的星系的激发特性:没有电离光子大量逃逸的证据

Excitation properties of galaxies with the highest [OIII]/[OII] ratios: No evidence for massive escape of ionizing photons

G. Stasinska, Yu. Izotov, C. Morisset, N. Guseva

摘要:

恒星形成星系可能泄漏电离光子的可能性是当今许多研究宇宙再电离的核心。我们测试这一假设的本地蓝色致密矮星系的非常高的激发。我们通过检查斯隆数字巡天的数据发布7和10的光谱来收集这样的星系样本。我们认为,可靠的结论不能单独基于强线,并采取一种策略,包括重要的弱线,如[OI]和高激发HeII和[ArIV]线。我们的分析是基于纯粹的观测图和光电离模型与精心挑选的发射线比图的比较。我们表明,光谱能量分布从目前的恒星星族合成模型不能解释所有的观测约束,这使我们模仿几种情况下,可以解释的数据。这些包括硬X射线或电击的额外存在。我们发现,只有电离约束模型(或电离光子逃逸分数低于10%的模型)能够同时解释所有的观测约束。

英文摘要:

The possibility that star-forming galaxies may leak ionizing photons is at the heart of many present-day studies that investigate the reionization of the Universe. We test this hypothesis on local blue compact dwarf galaxies of very high excitation. We assembled a sample of such galaxies by examining the spectra from Data Releases 7 and 10 of the Sloan Digital Sky Survey. We argue that reliable conclusions cannot be based on strong lines alone, and adopt a strategy that includes important weak lines such as [OI] and the high-excitation HeII and [ArIV] lines. Our analysis is based on purely observational diagrams and on a comparison of photoionization models with well-chosen emission-line ratio diagrams. We show that spectral energy distributions from current stellar population synthesis models cannot account for all the observational constraints, which led us to mimick several scenarios that could explain the data. These include the additional presence of hard X-rays or of shocks. We find that only ionization-bounded models (or models with an escape fraction of ionizing photons lower than 10%) are able to simultaneously explain all the observational constraints.

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