Title: On the use of semi-numerical simulations in predicting the 21-cm signal from the epoch of reionization Show Chinese title

Title: 在利用半数值模拟预测再电离时期21厘米信号中的应用

Abstract: We perform a detailed comparison of three different simulations of the neutral hydrogen distribution during the epoch of reionization (EoR). Our benchmark is a radiative transfer simulation (C2RAY). Such simulations can produce realistic results, but are computationally expensive. We compare it with two different semi-numerical techniques: one using the same halos as C2RAY as its sources (Sem-Num), and one using a conditional Press-Schechter scheme (CPS+GS). These are more computationally efficient than C2RAY, but use more simplistic physics. We evaluate them in terms of how well they can reproduce the history and morphology of EoR. We find that Sem-Num can produce an ionization history and morphology that is very close to C2RAY. Considering the effects of redshift space distortions due to peculiar velocities, we also study a number of statistics such as: the variance, spherically averaged power spectrum and various angular multipole moments of the power spectrum of the 21-cm signal from EoR,that will be observable by upcoming radio telescopes. We find that both semi-numerical models perform quite well in predicting these observables at length scales relevant for the present and future experiments. We also observe that predictions from Sem-Num are slightly better (by $\sim 10\%$) than CPS+GS for most of the observables. However, the predictions for the reionization history and the morphology of the ionization maps are significantly better (by $\sim 25-50\%$) in Sem-Num than CPS+GS. As the predictions for the 21-cm signal together with the reionization history would be required for parametrization of EoR from the observations, it would be better to use a semi-numerical simulation which can predict both with an acceptable accuracy. Our analysis shows that among the two semi-numerical simulations Sem-Num satisfies this criteria very well as it uses a source model very similar to C2RAY. Show Chinese abstract

Abstract: 我们对再电离时期（EoR）中中性氢分布的三种不同模拟进行了详细比较。 我们的基准是辐射转移模拟（C2RAY）。 这些模拟可以产生现实的结果，但计算成本很高。 我们将它与两种不同的半数值技术进行比较：一种使用与C2RAY相同的晕作为其源（Sem-Num），另一种使用条件Press-Schechter方案（CPS+GS）。 这些方法比C2RAY计算效率更高，但使用的物理模型更简单。 我们评估它们在多大程度上能够再现EoR的历史和形态。 我们发现，Sem-Num可以产生与C2RAY非常接近的电离历史和形态。 考虑到由于特殊速度引起的红移空间畸变的影响，我们还研究了一些统计量，例如：21厘米信号的方差、球对称平均功率谱以及功率谱的各种角度多重极矩，这些将是未来射电望远镜可观察到的。 我们发现，这两种半数值模型在预测当前和未来实验相关尺度上的这些可观测值方面表现相当不错。 我们还观察到，对于大多数可观测值，Sem-Num的预测略优于CPS+GS（由$\sim 10\%$表示）。 然而，对于再电离历史和电离图的形态，Sem-Num的预测显著优于CPS+GS（由$\sim 25-50\%$表示）。 由于从观测中对EoR进行参数化需要21厘米信号和再电离历史的预测，因此最好使用一种可以以可接受精度预测两者的半数值模拟。 我们的分析表明，在两种半数值模拟中，Sem-Num很好地满足了这一标准，因为它使用的源模型与C2RAY非常相似。