The effects of radiative transfer on the reionization of an inhomogeneous universe
The effects of radiative transfer on the reionization of an inhomogeneous universe
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辐射传输对非均匀宇宙再电离的影响
DOI：
10.1046/j.1365-8711.2001.04008.x
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发表时间：
2001
影响因子：
4.8
通讯作者：
H. Susa
中科院分区：
文献类型：
--
作者：
T. Nakamoto;M. Umemura;H. Susa
假设密度涨落增长的动力学简单，我们实施六维（6D）辐射传输计算，以阐明非均匀宇宙再电离过程中光子传播的影响。在本文中，电离源被假设为类活动星系核。目前的模拟表明，在渗流时期之后，辐射传输效应仍然相当显着，其中斑片状电离区域相互连接。换句话说，由于集体不透明，即使强烈的自屏蔽区域消失，宇宙也不会变得对电离辐射完全透明。事实证明，介质的不均匀性增强了不透明效应并延迟了再电离的结束。由于这种辐射转移效应，与均匀宇宙中迅速的再电离相比，非均匀宇宙中的再电离进行得相当缓慢，因此再电离的表面不是那么尖锐，而是高度不均匀。作为再电离表面不平坦的特征，由辐射复合产生的 Lyα 光子产生的宇宙红外背景（CIB）辐射可能表现出强烈的各向异性，反映了再电离时代密度波动的幅度。预测的 CIB 强度取决于即将推出的红外太空望远镜设施可能检测到的水平。
Assuming simple dynamics for the growth of density fluctuations, we implement six-dimensional (6D) radiative transfer calculations to elucidate the effects of photon propagation during the reionization of an inhomogeneous universe. The ionizing sources are postulated to be AGN-like in this paper. The present simulations reveal that radiative transfer effects are still prominent considerably after the percolation epoch, in which patchy ionized regions connect with each other. In other words, owing to the collective opacity, the Universe does not become perfectly transparent against ionizing radiation even though strongly self-shielded regions disappear. It turns out that the inhomogeneity of the medium enhances the opacity effects and delays the end of reionization. Owing to such radiative transfer effects, the reionization in an inhomogeneous universe proceeds fairly slowly, in contrast to the prompt reionization in a homogeneous universe, and as a result the surface of reionization is not so sharply edged, but highly uneven. As a signature of the uneven surface of reionization, the cosmic IR background (CIB) radiation, which is produced by Lyα photons resulting from radiative recombination, could exhibit strong anisotropies, reflecting the amplitude of density fluctuations at the reionization era. The predicted CIB intensity lies on a level of possible detection by forthcoming IR space telescope facilities.