The Earliest Luminous Sources and the Damping Wing of the Gunn-Peterson Trough
The Earliest Luminous Sources and the Damping Wing of the Gunn-Peterson Trough
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最早的发光源和冈恩-彼得森海槽的阻尼翼
DOI：
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发表时间：
2000
期刊：
影响因子：
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通讯作者：
M. Rees
中科院分区：
文献类型：
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作者：
P. Madau;M. Rees
最近对高红移星系和类星体的观测表明，星际介质(IGm)的氢成分一定是在某个红移z≳6处重新电离的。在完全重新电离之前，在仍然是中性的中间气体后面会看到紫外线辐射源，它们的光谱应该显示出冈恩-彼得森海槽的红色阻尼翼。虽然这一特征原则上可以完全抑制宇宙中第一代天体光谱中的Lyα发射线，但我们在这里表明，由于莱曼连续光子的源发射，发光类星体附近的IGM将在几个兆秒尺度上被高度光致电离。如果类星体的寿命短于膨胀和气体复合时间，则电离的体积将与13.6 eV以上产生的光子总数成正比；这种局域光电电离的效果是大大降低了类星体红移与其HⅡ区边界之间的散射不透明度。我们发现，对于总共辐射到α1069.5电离光子的源，Ly≳共振红边的透过率总是大于50%。因此，在发光时间为107年的明亮类恒星天体的光谱中探测到一条强的Lyα发射线不能单独用作对再电离时代的限制。在从中性宇宙到电离宇宙的转变之前，物体辐射的第一个迹象可能最好地在具有少量莱曼连续光子进入IGM的发光源或具有较短占空比的发光源的光谱中寻找。
Recent observations of high-redshift galaxies and quasars indicate that the hydrogen component of the intergalactic medium (IGM) must have been reionized at some redshift z ≳ 6. Prior to complete reionization, sources of ultraviolet radiation will be seen behind intervening gas that is still neutral, and their spectra should show the red damping wing of the Gunn-Peterson trough. While this characteristic feature may, in principle, totally suppress the Lyα emission line in the spectra of the first generation of objects in the universe, we show here that the IGM in the vicinity of luminous quasars will be highly photoionized on several megaparsec scales as a result of the source emission of Lyman continuum photons. If the quasar lifetime is shorter than the expansion and gas recombination timescales, the volume ionized will be proportional to the total number of photons produced above 13.6 eV; the effect of this local photoionization is to greatly reduce the scattering opacity between the redshift of the quasar and the boundary of its H II region. We find that the transmission on the red side of the Lyα resonance is always greater than 50% for sources radiating a total of ≳1069.5 ionizing photons into the IGM. The detection of a strong Lyα emission line in the spectra of bright quasi-stellar objects shining for ≳107 yr cannot then be used, by itself, as a constraint on the reionization epoch. The first signs of an object radiating prior to the transition from a neutral to an ionized universe may be best searched for in the spectra of luminous sources with a small escape fraction of Lyman continuum photons into the IGM or sources with a short duty cycle.