Excitation properties of galaxies with the highest [OIII]/[OII] ratios: No evidence for massive escape of ionizing photons
Excitation properties of galaxies with the highest [OIII]/[OII] ratios: No evidence for massive escape of ionizing photons
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DOI：
10.1051/0004-6361/201425389
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发表时间：
2015-03
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影响因子：
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通讯作者：
G. Stasińska;Y. Izotov;C. Morisset;N. Guseva
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文献类型：
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作者：
G. Stasińska;Y. Izotov;C. Morisset;N. Guseva
形成恒星的星系可能会泄漏电离光子的可能性，是当今许多研究宇宙再电离的研究的核心。我们在非常高激发的局部蓝致密矮星系上验证了这一假设。我们通过检查斯隆数字巡天第7和第10号数据发布的光谱，收集了这样一个星系的样本。我们认为，可靠的结论不能仅基于强谱线，并采用包括[OI]和高激发HeII和[ArIV]线等重要弱谱线的策略。我们的分析是基于纯粹的观测图和光电离模型与精心选择的发射在线比图的比较。我们表明，目前恒星群综合模型的光谱能量分布不能解释所有的观测限制，这导致我们模拟了几个可以解释数据的场景。这些包括硬x射线或冲击的额外存在。我们发现只有电离边界模型（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。
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.