光锥EoR 21 cm信号的模拟和量化
Towards simulating and quantifying the light-cone EoR 21-cm signal
摘要：
光锥（LC）效应导致再电离时期（EoR）21-cm信号$T_{\rm b} (\hat{\bf{n}}, ν)$沿着视线（LoS）方向$ν$显著地演变。在本文的第一部分中，我们提出了一种方法，适当地将LC效应的EoR 21厘米信号，包括奇特的速度的模拟。随后，我们讨论了如何量化的二阶统计的EoR 21厘米信号的LC效应的存在。我们证明了3D功率谱$P({\bf{k}})$未能量化整个信息，因为它假设信号是遍历和周期性的，而LC效应打破了这些条件沿LoS。考虑以红移$8$为中心的LC模拟，其中平均中性分数从$0.65$下降到$0.35$穿过盒子，我们发现$P({\bf{k}})$错过了$17.41 \, {\rm MHz}$模拟带宽两端的信息的$\sim 40 \%$。多频角功率谱（MAPS）${\mathcal C}_{\ell}(ν_1,ν_2)$量化了$T_{\rm b} (\hat{\bf{n}}, ν)$的统计特性，而不假设信号沿着LoS是遍历的和周期性的。我们希望这能量化EoR 21 cm信号的全部统计信息。我们应用MAPS我们的LC模拟和EoR 21厘米信号的初步结果。
英文摘要：
The light-cone (LC) effect causes the Epoch of Reionization (EoR) 21-cm signal $T_{\rm b} (\hat{\bf{n}}, ν)$ to evolve significantly along the line of sight (LoS) direction $ν$. In the first part of this paper, we present a method to properly incorporate the LC effect in simulations of the EoR 21-cm signal that include peculiar velocities. Subsequently, we discuss how to quantify the second order statistics of the EoR 21-cm signal in the presence of the LC effect. We demonstrate that the 3D power spectrum $P({\bf{k}})$ fails to quantify the entire information because it assumes the signal to be ergodic and periodic, whereas the LC effect breaks these conditions along the LoS. Considering a LC simulation centered at redshift $8$ where the mean neutral fraction drops from $0.65$ to $0.35$ across the box, we find that $P({\bf{k}})$ misses out $\sim 40 \%$ of the information at the two ends of the $17.41 \, {\rm MHz}$ simulation bandwidth. The multi-frequency angular power spectrum (MAPS) ${\mathcal C}_{\ell}(ν_1,ν_2)$ quantifies the statistical properties of $T_{\rm b} (\hat{\bf{n}}, ν)$ without assuming the signal to be ergodic and periodic along the LoS. We expect this to quantify the entire statistical information of the EoR 21-cm signal. We apply MAPS to our LC simulation and present preliminary results for the EoR 21-cm signal.
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