基于模拟的活动星系核喷流种群建模：实现黑洞喷流速度更稳健的对比
Simulation-based inference for AGN jet population modelling: Towards more robust comparisons of black hole jet speeds
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中文总结 AI 辅助
该研究采用无似然基于模拟的推理方法，修正AGN喷流速度参数估计的误差与非高斯性，得出AGN洛伦兹因子分布斜率，实现AGN与XRB喷流的更准确对比。
中文摘要 AI 辅助
我们采用无似然的基于模拟的推理方法，完成了对MOJAVE 1.5 Jansky Quarter Century活动星系核（AGN）喷流种群最完整的建模。由于流量限对观测到的AGN数据集存在复杂影响，需要对母种群进行仔细建模。特别是在观测并拟合多个数据分布时，似然函数会变得不直观；参数简并性进一步使问题复杂化，使其适用于无似然的基于模拟的推理。该方法依赖于归一化流直接学习似然曲面或后验分布。我们对该流进行了广泛验证，结果表明，先前对AGN喷流速度分布的参数估计显著低估了参数误差，且未捕捉到参数后验分布的非高斯性。新结果不仅能与其他AGN种群研究进行更优的统计对比，还能将超大质量黑洞喷流与质量更低的对应天体——X射线双星（XRB）进行更准确的对比。我们发现AGN的洛伦兹因子分布满足N(Γ) ∝ Γ^b，其中b=-1.32_{-0.19}^{+0.20}，该斜率与X射线双星洛伦兹因子分布在2σ水平上一致。基于模拟的推理作为一种方法，总体上非常适合许多天体物理问题，本文展示了该方法尤其适用于具有多个可观测量的喷流AGN母种群研究。
英文摘要
We present the most complete modelling of the MOJAVE 1.5 Jansky Quarter Century active galactic nuclei (AGN) jet population, using likelihood-free simulation-based inference. Due to the complex impact of a flux-limit on observed AGN data sets, careful modelling of the parent population is required. In particular, when observing and fitting to multiple data distributions likelihoods become non-intuitive. Parameter degeneracies further complicate the problem and make it suitable for likelihood-free, simulation-based inference. This method relies on a normalising flow learning the likelihood surface or posteriors directly. We extensively validate the flow to show that previous parameter estimates for the AGN jet speed distributions underestimated parameter errors significantly and do not capture the non-gaussianity of the parameter posteriors. The new results enable a better statistical comparison to other AGN population studies, but also a more accurate comparison of supermassive black hole jets with their lower mass counterparts, X-ray binaries (XRB). We find that the AGN follow a Lorentz factor distribution of the shape $N(Γ) \propto Γ^b$ with $b= -1.32_{-0.19}^{+0.20}$. This slope is consistent with the XRB Lorentz factor distribution at $2σ$. Simulation-based inference as a method is generally well-suited to many astrophysical problems, and this paper shows the convenient applicability of this methodology to parent population studies of jetted AGN with multiple observables specifically.
