膨胀宇宙的几何效应对高红移冷中性气体探测的影响
The geometry effects of an expanding Universe on the detection of cool neutral gas at high redshift
摘要：
最近对阻尼莱曼-α吸收系统（DLAs）中21 cm吸收的高红移调查，在z > 2到25处进行了公开的搜索，与z < 2处的搜索数量相同，尽管高红移的检测率仍然显着较低（20% cf. 60%）。使用已知的性质的DLAs来估计未知的轮廓宽度的21厘米非检测和包括通过生存分析的限制，我们表明，平均自旋温度/覆盖因子简并在高红移是，平均而言，两倍的低红移样品。这个值明显低于先前自旋温度的8倍，并且与低和高红移样本之间的角直径距离比的因子大致相同。也就是说，不需要几个关键的假设，这导致了自旋温度的演变，我们表明，所观察到的分布的21厘米探测器在DLAs可以占一个膨胀的宇宙的几何效应。也就是说，到目前为止，还没有证据表明富含气体的星系的自旋温度随红移而演化。
英文摘要：
Recent high redshift surveys for 21-cm absorption in damped Lyman-alpha absorption systems (DLAs) take the number of published searches at z > 2 to 25, the same number as at z < 2, although the detection rate at high redshift remains significantly lower (20% cf. 60%). Using the known properties of the DLAs to estimate the unknown profile widths of the 21-cm non-detections and including the limits via a survival analysis, we show that the mean spin temperature/covering factor degeneracy at high redshift is, on average, double that of the low redshift sample. This value is significantly lower than the previous factor of eight for the spin temperatures and is about the same factor as in the angular diameter distance ratios between the low and high redshift samples. That is, without the need for the several pivotal assumptions, which lead to an evolution in the spin temperature, we show that the observed distribution of 21-cm detections in DLAs can be accounted for by the geometry effects of an expanding Universe. That is, as yet there is no evidence of the spin temperature of gas rich galaxies evolving with redshift.
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