用混合模型快速模拟宇宙黎明时期的21厘米信号，提升理论分析效率。
21cmEMUv3: a hybrid diffusion-LSTM emulator of 21cmFAST summary observables
- 结合扩散模型与LSTM网络，高精度模拟7类宇宙黎明观测量。
- 首次在宽红移范围（z=6–30）内实现柱状21cm功率谱的亚百分级准确模拟。
- 适合从事早期星系、射电宇宙学及平方公里阵列预研的研究者。
我们正迎来宇宙黎明（CD）与再电离时代（EoR）观测的爆发，推动对快速稳健理论解释框架的需求。为此，机器学习尤其是模拟器方法已成为加速和增强推断流程的强大工具。本文提出21cmEMUv3，一个基于21cmFASTv3模拟训练的模拟器，可建模原子冷却与分子冷却星系。该模拟器以σ₈和十个天体物理参数为条件，生成七类总结性观测量：(i) 柱状21cm功率谱（PS），首次在宽红移范围z∼6–30内实现高分辨率高精度模拟；(ii) 球对称平均21cm PS；(iii) 宇宙间介质（IGM）的平均中性分数；(iv) 平均21cm自旋温度；(v) 全局21cm信号；(vi) 紫外光度函数（LFs）；(vii) 汤姆孙散射光学深度。其中柱状21cm PS通过基于得分的扩散模型模拟，其余六项采用长短期记忆（LSTM）网络，均达到亚百分级中位数精度。我们利用该模拟器重新解读来自HERA的当前21cm PS上限，首次引入最先进的流体动力学模拟来约束分子冷却星系内的恒星形成先验。结果表明，我们的软带X射线光度率每单位恒星形成速率在95%置信水平下排除低于10³⁹·² erg s⁻¹ M⁻¹_⊙ yr⁻¹的值。最后，我们针对不同阵列配置预测了平方公里阵列（SKA）探测21cm PS的前景。21cmEMU代码已公开。
原文摘要 · Abstract (English)
We are witnessing a surge in observations of the cosmic dawn (CD) and epoch of reionisation (EoR), driving an increasing demand for fast and robust theoretical interpretation frameworks. In response, machine learning (ML), and emulation in particular, has emerged as a powerful approach to accelerate and enhance inference pipelines. In this work, we present 21cmEMUv3, an emulator trained on 21cmFASTv3 simulations that model both atomically and molecularly cooling galaxies. 21cmEMUv3 is conditioned on $σ_8$ and ten astrophysical parameters to produce seven summary observables: (i) the cylindrical 21cm power spectrum (PS), emulated for the first time at such high resolution and accuracy across a wide redshift range of $z \sim$ 6--30; (ii) the spherically-averaged 21cm PS; (iii) the mean neutral fraction of the intergalactic medium (IGM); (iv) the mean 21cm spin temperature; (v) the global 21cm signal; (vi) the ultraviolet (UV) luminosity functions (LFs); and (vii) the Thomson scattering optical depth. Notably, the cylindrical 21cm PS is emulated via score-based diffusion, while the remaining six summaries are emulated via long-short term memory (LSTM) networks, all achieving sub-percent median accuracy. We use the emulator to reinterpret current 21cm PS upper limits from HERA, for the first time using state-of-the-art hydrodynamical simulations to inform priors on star formation inside molecularly cooling galaxies. We find that our inferred soft-band X-ray luminosity per unit star formation rate is consistent with extrapolations of high-mass X-ray binaries to the low-metallicity regimes expected in the first galaxies, excluding values below $10^{39.2}$ erg s$^{-1}M^{-1}_\odot \rm{yr}$ at $95\%$ confidence. Finally, we produce forecasts for the detection of the cosmic 21cm PS with the Square Kilometre Array for different array configurations. The 21cmEMU package is publicly available.
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