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首页> 外文期刊>PASJ: Publications of the Astronomical Society of Japan >Probing intergalactic neutral hydrogen by the Lyman alpha red damping wing of gamma-ray burst 130606A afterglow spectrum at z = 5.913
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Probing intergalactic neutral hydrogen by the Lyman alpha red damping wing of gamma-ray burst 130606A afterglow spectrum at z = 5.913

机译：用γ射线爆发130606A的余辉光谱的莱曼阿尔法红阻尼翼探测银河系中性氢，z = 5.913

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摘要

The unprecedentedly bright optical afterglow of GRB130606A located by Swift at a redshift close to the reionization era (z = 5.913) provides a new opportunity to probe the ionization status of the intergalactic medium (IGM). Here we present an analysis of the red Lyα damping wing of the afterglow spectrum taken by Subaru/FOCAS during 10.4–13.2 hr after the burst. We find that the minimal model including only the baseline power-law and HI absorption in the host galaxy does not give a good fit, leaving residuals showing concave curvature in 8400–8900 °A with an amplitude of about 0.6% of the flux. Such a curvature in the short wavelength range cannot be explained either by extinction at the host with standard extinction curves, intrinsic curvature of afterglow spectra, or by the known systematic uncertainties in the observed spectrum. The red damping wing by intervening HI gas outside the host can reduce the residual by about 3 σ statistical significance. We find that a damped Lyα system is not favored as the origin of this intervening HI absorption, from the observed Lyβ and metal absorption features. Therefore absorption by diffuse IGM remains as a plausible explanation. A fit by a simple uniform IGM model requires an HI neutral fraction of f_(HI) ~ 0.1–0.5 depending on the distance to the GRB host, implying high fHI IGM associated with the observed dark Gunn–Peterson (GP) troughs. This gives new evidence that the reionization is not yet complete at z = 6.
机译：Swift所记录的GRB130606A空前明亮的光学余辉，在接近电离时代的红移处（z = 5.913），为探索星系间介质（IGM）的电离状态提供了新的机会。在这里，我们对斯巴鲁/ FOCAS在爆发后的10.4-13.2小时内拍摄的余辉光谱的红色Lyα阻尼翼进行了分析。我们发现，仅包含基线幂律和主星系中的HI吸收的最小模型不能很好地拟合，在8400–8900°A时残留量显示出凹曲率，其振幅约为通量的0.6％。在短波长范围内的这种曲率，既不能通过使用标准消光曲线在主体处消光，余辉光谱的固有曲率，也不能通过观察到的光谱中已知的系统不确定性来解释。通过在主机外部插入HI气体，红色阻尼翼可将残余量减少3σ统计显着性。我们发现，从观察到的Lyβ和金属吸收特征来看，阻尼的Lyα系统不适合作为这种中间HI吸收的来源。因此，弥散IGM的吸收仍然是一个合理的解释。通过简单的统一IGM模型进行拟合需要HI中性分数f_（HI）〜0.1–0.5，具体取决于与GRB宿主的距离，这意味着与观察到的深色Gunn-Peterson（GP）谷相关的高fHI IGM。这提供了新的证据，表明在z = 6时电离尚未完成。

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