用神经网络快速模拟星系内禀对齐,提升弱引力透镜分析精度。
IAEmu: Learning Galaxy Intrinsic Alignment Correlations
- 基于霍德框架的模拟数据训练神经网络,预测三种相关函数。
- 对ξ误差仅3%,ω误差5%,且能捕捉η的随机性。
- 速度提升一万倍,适合大型巡天的反演建模研究。
星系内禀对齐(IA)是弱引力透镜分析中的关键干扰源,源于潮汐相互作用和星系形成过程引起的星系形状相关性。准确建模IA对稳健的宇宙学推断至关重要,但现有方法依赖于在非线性尺度失效的微扰理论或计算昂贵的模拟。本文提出IAEmu,一种基于神经网络的代理模型,利用基于晕占有分布(HOD)框架的模拟星系样本,预测星系位置-位置(ξ)、位置-取向(ω)和取向-取向(η)相关函数及其不确定性。相比模拟,IAEmu对ξ的平均误差约为3%,对ω约为5%,同时在不过拟合的情况下捕捉η的随机性。该模型提供认知不确定性和随机不确定性,有助于识别预测可靠性较低的区域。我们还展示了其在非HOD对齐信号上的泛化能力,通过拟合IllustrisTNG流体动力学模拟数据验证。作为全可微神经网络,IAEmu在GPU上实现约10,000倍的速度提升,相较于基于CPU的模拟,显著加速了从HOD参数到相关函数的映射,支持基于梯度的采样反演建模,为第四代弱引力透镜巡天提供强大工具。
原文摘要 · Abstract (English)
The intrinsic alignments (IA) of galaxies, a key contaminant in weak lensing analyses, arise from correlations in galaxy shapes driven by tidal interactions and galaxy formation processes. Accurate IA modeling is essential for robust cosmological inference, but current approaches rely on perturbative methods that break down on nonlinear scales or on expensive simulations. We introduce IAEmu, a neural network-based emulator that predicts the galaxy position-position ($ξ$), position-orientation ($ω$), and orientation-orientation ($η$) correlation functions and their uncertainties using mock catalogs based on the halo occupation distribution (HOD) framework. Compared to simulations, IAEmu achieves ~3% average error for $ξ$ and ~5% for $ω$, while capturing the stochasticity of $η$ without overfitting. The emulator provides both aleatoric and epistemic uncertainties, helping identify regions where predictions may be less reliable. We also demonstrate generalization to non-HOD alignment signals by fitting to IllustrisTNG hydrodynamical simulation data. As a fully differentiable neural network, IAEmu enables $\sim$10,000$\times$ speed-ups in mapping HOD parameters to correlation functions on GPUs, compared to CPU-based simulations. This acceleration facilitates inverse modeling via gradient-based sampling, making IAEmu a powerful surrogate model for galaxy bias and IA studies with direct applications to Stage IV weak lensing surveys.
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