Emulating Simulations of Cosmic Dawn for 21cm Power Spectrum Constraints on Cosmology, Reionization, and X-Ray Heating
Emulating Simulations of Cosmic Dawn for 21cm Power Spectrum Constraints on Cosmology, Reionization, and X-Ray Heating
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DOI：
10.3847/1538-4357/aa8bb4
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发表时间：
2017-10-10
影响因子：
4.9
通讯作者：
Greig, Bradley
中科院分区：
文献类型：
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作者：
Kern, Nicholas S.;Liu, Adrian;Greig, Bradley
目前和即将进行的无线电干涉测量实验旨在对跨越宇宙氢再电离和X射线加热时期的高红移21厘米波动信号进行统计表征。然而，连接21厘米的统计数据的基础物理参数是复杂的理论挑战，建模的计算速度足够快，使探索的高维和弱约束的参数空间的相关物理。在这项工作中，我们使用机器学习算法来构建一个快速仿真器，该仿真器可以在很宽的参数空间内准确地模拟21 cm信号的昂贵仿真。我们将我们的模拟器嵌入到马尔可夫链蒙特卡罗框架中，以便在大量的模型参数上执行贝叶斯参数约束，包括那些管理再电离时代，X射线加热时代和宇宙学的参数。作为一个工作的例子，我们使用我们的仿真器来呈现一个更新的参数约束预测的氢时代的再电离阵列实验，表明其特征的基准21厘米功率谱将大大缩小允许的参数空间的再电离和加热参数，并可能有助于加强普朗克的约束sigma（8）。我们提供了我们的广义仿真器代码和它的实现，特别是21厘米的参数约束作为公开可用的软件。
Current and upcoming radio interferometric experiments are aiming to make a statistical characterization of the high-redshift 21 cm fluctuation signal spanning the hydrogen reionization and X-ray heating epochs of the universe. However, connecting 21 cm statistics to the underlying physical parameters is complicated by the theoretical challenge of modeling the relevant physics at computational speeds quick enough to enable exploration of the high-dimensional and weakly constrained parameter space. In this work, we use machine learning algorithms to build a fast emulator that can accurately mimic an expensive simulation of the 21 cm signal across a wide parameter space. We embed our emulator within a Markov Chain Monte Carlo framework in order to perform Bayesian parameter constraints over a large number of model parameters, including those that govern the Epoch of Reionization, the Epoch of X-ray Heating, and cosmology. As a worked example, we use our emulator to present an updated parameter constraint forecast for the Hydrogen Epoch of Reionization Array experiment, showing that its characterization of a fiducial 21 cm power spectrum will considerably narrow the allowed parameter space of reionization and heating parameters, and could help strengthen Planck's constraints on sigma(8). We provide both our generalized emulator code and its implementation specifically for 21 cm parameter constraints as publicly available software.