Simulating cosmic reionization: how large a volume is large enough?
Simulating cosmic reionization: how large a volume is large enough?
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DOI：
10.1093/mnras/stt2497
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发表时间：
2013-10
影响因子：
4.8
通讯作者：
I. Iliev;G. Mellema;K. Ahn;P. Shapiro;Y. Mao;U. Pen
中科院分区：
文献类型：
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作者：
I. Iliev;G. Mellema;K. Ahn;P. Shapiro;Y. Mao;U. Pen
我们提出了迄今为止最大体积（425 Mpc h（-1）= 607 Mpc的一侧）的宇宙再电离的全辐射传输模拟。我们表明，在非常大的尺度上，密度波动有显着的额外的权力。我们系统地研究了这种额外的功率对再电离的进程、持续时间和特征以及对选定的再电离观测量的影响。我们发现，类似于100 Mpc h（-1）每边的共动体积是足够的，推导出一个收敛的平均再电离历史，但再电离斑块被显着低估。我们使用折刀分裂来量化再电离性质与模拟体积的收敛性。我们发现，除了最早的时间，每边近似100 Mpc h（-1）或更大的子体积产生收敛的再电离历史，但类似于50 Mpc h（-1）或更小的体积在任何红移都不能很好地收敛。再电离历史里程碑显示子体积之间的显著分散，对于类似于50 Mpc h（-1）的体积，高达类似于1的Δ z。如果我们仅考虑平均密度子区域，则散射减小，但是对于不同尺寸的子体积，保持在类似于0.1-0.2的Δ z。因此，许多潜在的再电离观测值，如21厘米均方根，21厘米PDF偏度和峰度都表现出良好的收敛体积类似于200 Mpc h（-1），但保留相当大的分散较小的体积。相比之下，在大尺度（k < 0.25 h Mpc（-1））的三维21-cm功率谱不完全收敛的任何子体积的大小。这些额外的大尺度波动大大增强了21厘米的波动，这将大大改善探测的前景，因为前景较低，干涉仪在较高频率下的灵敏度较高。
We present the largest-volume (425 Mpc h(-1) = 607 Mpc on a side) full radiative transfer simulation of cosmic reionization to date. We show that there is significant additional power in density fluctuations at very large scales. We systematically investigate the effects this additional power has on the progress, duration and features of reionization and on selected reionization observables. We find that comoving volume of similar to 100 Mpc h(-1) per side is sufficient for deriving a convergent mean reionization history, but that the reionization patchiness is significantly underestimated. We use jackknife splitting to quantify the convergence of reionization properties with simulation volume. We find that sub-volumes of similar to 100 Mpc h(-1) per side or larger yield convergent reionization histories, except for the earliest times, but smaller volumes of similar to 50 Mpc h(-1) or less are not well converged at any redshift. Reionization history milestones show significant scatter between the sub-volumes, as high as Delta z similar to 1 for similar to 50 Mpc h(-1) volumes. If we only consider mean-density sub-regions the scatter decreases, but remains at Delta z similar to 0.1-0.2 for the different size sub-volumes. Consequently, many potential reionization observables like 21-cm rms, 21-cm PDF skewness and kurtosis all showgood convergence for volumes of similar to 200 Mpc h(-1), but retain considerable scatter for smaller volumes. In contrast, the three-dimensional 21-cm power spectra at large scales (k < 0.25 h Mpc(-1)) do not fully converge for any sub-volume size. These additional large-scale fluctuations significantly enhance the 21-cm fluctuations, which should improve the prospects of detection considerably, given the lower foregrounds and greater interferometer sensitivity at higher frequencies.