球面上非局域随机场级星系偏差的解析模型
An analytical model for non-local stochastic field-level galaxy bias on the sphere
- Durham University（杜伦大学）
- University College London（伦敦大学学院）
- Leiden University（莱顿大学）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本文提出了BOLTS解析星系偏差模型，其在线性阶纳入随机性与非局域性，可准确再现两点统计与等边双谱，能为未来星系巡天提供高效场级正向建模，提升了星系偏差建模的准确性。
AI中文摘要：
我们提出了“球面上大尺度示踪剂中的过密区偏差”（BOLTS）模型，这是一种用于球面上投影场的新型解析星系偏差模型，其在线性阶就已纳入随机性与非局域性，同时保证了物理性与统计各向同性。我们未将星系偏差建模为确定性传递函数，而是将其建模为统计各向同性随机场，使随机性可通过偏差本身的涨落引入。该构造在调和空间中明确分解为线性、非局域随机及确定性分量。我们将模型参数拟合至大体积流体动力学模拟（FLAMINGO）中测得的投影功率谱，从而能在以星系属性（如晕质量或红移）为条件时，从模拟物质场中采样星系种群。基于构造，该模型可再现至模拟分辨率的两点统计；且在未对其进行校准的情况下，BOLTS 能在红移 0 < z < 3、晕质量 M_h > 10^11.5 M⊙ 的共动尺度 O(10 Mpc) 内，于模拟的样本方差内恢复等边双谱。相较于局域偏差方案，在示踪剂的随机性超过其离散性的所有场景（包括低红移及非线性效应变得重要的低晕质量 M_h = 10^11.5 M⊙）中，该模型能更准确地捕获测得的小波相位谐波中的振幅-相位关联与模式耦合。该模型可为基于模拟的推断及与 Euclid、Rubin LSST、Roman 等未来星系巡天的大型数据集的模型比较提供高效的场级正向建模，同时相比标准线性确定性模型提升了星系偏差建模的准确性。
英文摘要：
We present the `Bias of Overdensities in Large-scale Tracers on the Sphere' (BOLTS) model, a novel analytic galaxy bias model for projected fields on the sphere that incorporates stochasticity and non-locality already at linear order while enforcing physicality and statistical isotropy. Rather than as a deterministic transfer function, we model galaxy bias as a statistically isotropic random field, allowing stochasticity to enter through fluctuations in the bias itself. The construction yields an explicit decomposition into a linear, non-local stochastic and deterministic components in harmonic space. We fit the model parameters to the projected power spectra measured in large-volume hydrodynamical simulations (FLAMINGO), enabling sampling of galaxy populations from simulated matter fields while conditioning on galaxy properties such as halo mass or redshift. By construction, the model reproduces the two-point statistics down to the simulation resolution, and without being calibrated on it, BOLTS recovers the equilateral bispectrum within the sample variance of the simulation down to comoving scales of $\mathcal{O}(10 \, \mathrm{Mpc})$ for halo masses $ M_{\rm{h}} > 10^{11.5}\,\rm{M}_{\odot} $ over redshifts $0 < z < 3$. Relative to local bias prescriptions, it more accurately captures amplitude-phase correlations and mode coupling in the measured wavelet phase harmonics wherever the stochasticity of the tracers exceeds their discreteness, including low redshifts and lower halo masses $M_{\rm{h}} = 10^{11.5}\,\rm{M}_{\odot}$ where non-linearities become important. This model enables efficient field-level forward modelling for simulation-based inference and model comparison with large datasets from forthcoming galaxy surveys including Euclid, Rubin LSST, and Roman, while improving the accuracy of galaxy bias modelling with respect to standard linear deterministic models.
