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arXiv 1402.4429astro-ph.GAastro-ph.CO
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豌豆星系中电离光子的起源和光学深度

The Origin and Optical Depth of Ionizing Photons in the Green Pea Galaxies

A. E. Jaskot, M. S. Oey

摘要:

我们对高红移星系中辐射反馈和恒星形成的理解受到低红移星系中类似系统的稀有性的阻碍。然而,最近发现的绿豌豆(GP)星系在形态和恒星形成率方面与高红移星系相似,是探测电离光子产生和传输的重要工具。GPS包含大量的星团,它们发出大量的高能辐射,如强烈的[OIII] 5007发射和HeII 4686发射所示。我们重点研究了6个[O III] 5007,4959/[O II] 3727 ~10或更高比值的GP星系。如此高的比率指示具有高电离参数或低光学深度的气体。GP线的比率和年龄指向化学均匀的大质量恒星,沃尔夫-拉叶星,或冲击电离作为最有可能的来源,他II的排放。包括冲击电离在内的模型表明,GP可能具有较低的光学深度,这与电离光子沿着最近超新星产生的通道逃逸的情况一致。GP和类似的星系可以通过揭示电离光子如何从大质量星团传播到星系际介质来揭示宇宙再电离的新情况。

英文摘要:

Our understanding of radiative feedback and star formation in galaxies at high redshift is hindered by the rarity of similar systems at low redshift. However, the recently identified Green Pea (GP) galaxies are similar to high-redshift galaxies in their morphologies and star formation rates and are vital tools for probing the generation and transmission of ionizing photons. The GPs contain massive star clusters that emit copious amounts of high-energy radiation, as indicated by intense [OIII] 5007 emission and HeII 4686 emission. We focus on six GP galaxies with high ratios of [O III] 5007,4959/[O II] 3727 ~10 or more. Such high ratios indicate gas with a high ionization parameter or a low optical depth. The GP line ratios and ages point to chemically homogeneous massive stars, Wolf-Rayet stars, or shock ionization as the most likely sources of the He II emission. Models including shock ionization suggest that the GPs may have low optical depths, consistent with a scenario in which ionizing photons escape along passageways created by recent supernovae. The GPs and similar galaxies can shed new light on cosmic reionization by revealing how ionizing photons propagate from massive star clusters to the intergalactic medium.

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