The impact of inhomogeneous subgrid clumping on cosmic reionization: II. Modelling stochasticity
The impact of inhomogeneous subgrid clumping on cosmic reionization: II. Modelling stochasticity
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不均匀亚网格聚集对宇宙再电离的影响：II。
DOI：
10.1093/mnras/stab787
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发表时间：
2021
影响因子：
4.8
通讯作者：
Shapiro Paul R
中科院分区：
文献类型：
--
作者：
Bianco Michele;Iliev Ilian T;Ahn Kyungjin;Giri Sambit K;Mao Yi;Park Hyunbae;Shapiro Paul R
小尺度的密度波动可以显著地影响再电离，但通常模型相当粗糙。数值模拟和分析计算中未解决的波动包括使用气聚因子，通常假设是独立的本地环境。在论文I中，我们提出了一个改进的，局部密度相关的亚网格气体聚集模型。在这里，我们使用一个经验随机模型的基础上，从高分辨率的数值模拟，完全解决所有相关的波动的结果。我们的模型再现以及平均密度成团关系和它的分散。我们应用我们的随机模型，沿着的平均聚团和纸我确定性模型，创建大体积实现的聚团场，并使用这些在宇宙再电离的辐射传输模拟。我们的研究结果表明，简单化的平均聚集模型延迟再电离相比，当地的密度依赖模型，尽管产生较少的重组整体。这是由于聚集的空间分布非常不同，导致在后一种情况下光电离率高得多。平均聚集模型在大部分再电离过程中产生较小的Hiregions，但这些区域在后期渗透得更快。它还导致21 cm波动峰值的显著延迟，并在PDF分布中产生较低的非高斯性和更少的亮像素。随机密度依赖模型显示出与确定性模型相对较小的差异，主要集中在重叠周围，在那里它显着抑制21 cm波动，以及在21 cm PDF的明亮尾部，在那里它产生明显更明亮的像素。
Small-scale density fluctuations can significantly affect reionization, but are typically modelled quite crudely. Unresolved fluctuations in numerical simulations and analytical calculations are included using a gasclumping factor, typically assumed to be independent of the local environment. In Paper I, we presented an improved, local density-dependent model for the sub-grid gas clumping. Here, we extend this using anempirical stochastic modelbased on the results from high-resolution numerical simulations which fully resolve all relevant fluctuations. Our model reproduces well both the mean density-clumping relation and its scatter. We applied our stochastic model, along with the mean clumping one and the Paper I deterministic model, to create large-volume realizations of the clumping field, and used these in radiative transfer simulations of cosmic reionization. Our results show that the simplistic mean clumping model delays reionization compared to local density-dependent models, despite producing fewer recombinations overall. This is due to the very different spatial distribution of clumping, resulting in much higher photoionization rates in the latter cases. The mean clumping model produces smaller Hiiregions throughout most of reionization, but those percolate faster at late times. It also causes a significant delay in the 21-cm fluctuations peak and yields lower non-Gaussianity and many fewer bright pixels in the PDF distribution. The stochastic density-dependent model shows relatively minor differences from the deterministic one, mostly concentrated around overlap, where it significantly suppresses the 21-cm fluctuations, and at the bright tail of the 21-cm PDFs, where it produces noticeably more bright pixels.