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arXiv 1009.4697astro-ph.CO
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原初氢复合中的辐射转移效应

Radiative transfer effects in primordial hydrogen recombination

Yacine Ali-Haïmoud, Daniel Grin, Christopher M. Hirata

摘要:

高精度宇宙复合历史的计算是近年来人们特别关注的问题,因为它是预测宇宙微波背景各向异性角功率谱的主要理论不确定性因素。莱曼跃迁,特别是莱曼-α线,由于其非常低的逃逸概率,长期以来一直被认为是复合的瓶颈之一。Sobolev近似不能以足够的精度描述莱曼线附近的辐射转移,并且在其他工作中已经计算了几个校正。本文计算了一些以前忽略的辐射转移效应的影响。首先,汤姆逊散射在莱曼α线附近的效果进行评估,使用一个完整的再分配内核纳入辐射转移代码。本文用解析近似法研究了氢线蓝向的光学厚氘莱曼α线产生畸变的反馈效应。结果表明,在宇宙学氢复合过程中,这两种效应都可以忽略不计。其次,高的重要性,非重叠莱曼过渡进行了评估。它示出,从以上的Ly-gamma和Ly-beta和更高的线的频率扩散线逃逸可以忽略不计的准确性损失。第三,一种形式主义概括的Sobolev近似的开发占的重叠的高躺莱曼线,这是导致可以忽略不计的变化的重组历史。最后,探讨了宇宙学氢复合脉泽的可能性。结果表明,在这里提出的纯辐射处理中不存在这样的脉塞。

英文摘要:

The calculation of a highly accurate cosmological recombination history has been the object of particular attention recently, as it constitutes the major theoretical uncertainty when predicting the angular power spectrum of Cosmic Microwave Background anisotropies. Lyman transitions, in particular the Lyman-alpha line, have long been recognized as one of the bottlenecks of recombination, due to their very low escape probabilities. The Sobolev approximation does not describe radiative transfer in the vicinity of Lyman lines to a sufficient degree of accuracy, and several corrections have already been computed in other works. In this paper, the impact of some previously ignored radiative transfer effects is calculated. First, the effect of Thomson scattering in the vicinity of the Lyman-alpha line is evaluated, using a full redistribution kernel incorporated into a radiative transfer code. The effect of feedback of distortions generated by the optically thick deuterium Lyman-alpha line blueward of the hydrogen line is investigated with an analytic approximation. It is shown that both effects are negligible during cosmological hydrogen recombination. Secondly, the importance of high-lying, non overlapping Lyman transitions is assessed. It is shown that escape from lines above Ly-gamma and frequency diffusion in Ly-beta and higher lines can be neglected without loss of accuracy. Thirdly, a formalism generalizing the Sobolev approximation is developed to account for the overlap of the high-lying Lyman lines, which is shown to lead to negligible changes to the recombination history. Finally, the possibility of a cosmological hydrogen recombination maser is investigated. It is shown that there is no such maser in the purely radiative treatment presented here.

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