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arXiv 1105.3207astro-ph.CO
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超新星对宇宙再电离的贡献

The Contribution of Supernovae to Cosmic Reionization

Jarrett L. Johnson, Sadegh Khochfar

摘要:

虽然恒星被广泛讨论为使宇宙再电离的高能光子的来源,但在这种情况下,另一个电离光子的来源也必须有助于再电离,这是标志着大质量恒星生命结束的超新星(SNe)。在这里,我们估计SNe和恒星的相对贡献,再电离。虽然电离光子在SN冲击中产生的速率远低于它们由恒星产生的速率,但从SNe发射的辐射的较硬光谱导致SN产生的光子相对于恒星光子的逃逸分数增强。特别是,沿着星系外给定的视线,我们发现当中性氢柱密度N_H >~10^18 cm^-2时,SNe对再电离的贡献大于恒星。利用文献中的模拟结果,我们发现,整体(视线平均)SNe冲击产生的电离光子逃逸分数大于恒星光子逃逸分数的一个因素的\simeq 4到\simeq 7,取决于金属丰度的恒星星族。总的来说,我们的研究结果表明,SNe的效果是提高了约10%的恒星源再电离的氢的分数。我们简要地讨论了我们的研究结果的人口负责星系再电离的影响。

英文摘要:

While stars are widely discussed as the source of the high energy photons which reionized the universe, an additional source of ionizing photons that must also contribute to reionization in this scenario is the supernovae (SNe) which mark the end of the life of massive stars. Here we estimate the relative contributions of SNe and stars to reionization. While the rate at which ionizing photons are produced in SN shocks is well below that at which they are produced by stars, the harder spectra of radiation emitted from SNe leads to an enhanced escape fraction of SN generated photons relative to that of stellar photons. In particular, along a given line of sight out of a galaxy, we find that for neutral hydrogen column densities N_H >~10^18 cm^-2 the contribution to reionization from SNe is greater than that from stars. Drawing on the results of simulations presented in the literature, we find that the overall (line of sight-averaged) SNe shock-generated ionizing photon escape fraction is larger than the stellar photon escape fraction by a factor of \simeq 4 to \simeq 7, depending on the metallicity of the stellar population. Overall, our results suggest that the effect of SNe is an enhancement of up to ~ 10 percent in the fraction of hydrogen reionized by stellar sources. We briefly discuss the implications of our results for the population of galaxies responsible for reionization.

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