Can non‐Gaussian cosmological models explain the WMAP high optical depth for reionization?
Can non‐Gaussian cosmological models explain the WMAP high optical depth for reionization?
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DOI：
10.1111/j.1365-2966.2003.07316.x
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发表时间：
2003-09
影响因子：
4.8
通讯作者：
Xuelei Chen;A. Cooray;N. Yoshida;N. Sugiyama
中科院分区：
文献类型：
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作者：
Xuelei Chen;A. Cooray;N. Yoshida;N. Sugiyama
威尔金森微波各向异性探测器第一年的数据表明汤姆逊散射的光学深度很高，为0.17 ′ 0.04，这意味着宇宙在比以前预期的更早的时期被再电离。这种早期的再电离很可能是由第一批恒星的紫外线（UV）光子引起的，但似乎只有在早期宇宙中星星的形成非常有效的情况下，观察到的高光学深度才能在标准结构形成模型中得到调和。在正常的星星形成效率下，具有非高斯密度波动的宇宙学模型可能会避免这种冲突，因为高密度峰值比高斯波动模型在更早的时期崩溃。我们研究宇宙再电离在非高斯模型，并探讨在何种程度上，在现有的限制，非高斯影响再电离的历史。对于红移为30至50的温和非高斯波动，光学深度的增加保持在百分之几的水平，似乎不太可能帮助解释测量的高光学深度。另一方面，在现有的观测约束条件下，增加密度波动的非高斯性质可以很容易地再现光学深度，并可能在具有尺度依赖性的非高斯模型中保持可行性。
The first-year Wilkinson Microwave Anisotropy Probe data suggest a high optical depth for Thomson scattering of 0.17 ′ 0.04, implying that the Universe was reionized at an earlier epoch than previously expected. Such early reionization is likely to be caused by ultraviolet (UV) photons from first stars, but it appears that the observed high optical depth can be reconciled within the standard structure formation model only if star formation in the early Universe was extremely efficient. With normal star formation efficiencies, cosmological models with non-Gaussian density fluctuations may circumvent this conflict as high density peaks collapse at an earlier epoch than in models with Gaussian fluctuations. We study cosmic reionization in non-Gaussian models and explore to what extent, within available constraints, non-Gaussianities affect the reionization history. For mild non-Gaussian fluctuations at redshifts of 30 to 50, the increase in optical depth remains at a level of a few per cent and appears unlikely to aid significantly in explaining the measured high optical depth. On the other hand, within available observational constraints, increasing the non-Gaussian nature of density fluctuations can easily reproduce the optical depth and may remain viable in underlying models of non-Gaussianity with a scale-dependence.