AI 中文总结
以B1422+231为案例，研究非椭圆形状扰动（多极矩和径向变化）对图像位置和流量比的影响。从TNG100模拟提取扰动，用光滑宏观模型拟合，分析不同精度下扰动对模型拟合的作用，得出关于模型灵活性和简并性的经验。
AI 中文摘要
多重成像类星体透镜中的流量比异常是一个长期存在的问题。以经典系统B1422+231为例，我们研究了除椭圆形状之外的典型非团块状扰动——多极矩$m_3$、$m_4$以及$q$、$\phi_q$的径向变化——如何在不同观测精度下解释观测到的图像位置和流量比。我们从TNG100模拟中预先选择的强透镜星系样本中提取这些扰动。然后，将光滑宏观模型（SIE+$\gamma$，EPL+$\gamma$）仅拟合到观测到的图像位置，以及同时拟合位置和流量比，包括和不包括提取的扰动。当天文测量不确定度为$\sigma_{p}=10$ mas时，仅这两个宏观模型就已经能够在$3\sigma_{p}$范围内成功拟合图像位置。然而，当$\sigma_{p}=2$ mas时，如果仅采用光滑宏观模型，就会出现“天文测量异常”。在这种情况下，添加提取的扰动可以解释异常的图像位置。当同时采用位置和流量比时，SIE+$\gamma$模型族在光度测量不确定度$\sigma_{f} \le 10\%$（保持$\sigma_{p}=10$ mas）时就已经出现“流量比异常”。当使用EPL+$\gamma$时，仅光滑模型在$\sigma_{f}=10\%$、$5\%$时能够同时拟合位置和流量比，但在$\sigma_{f}=2\%$时不行，此时会出现‘流量比异常’。添加所有四种类型的提取扰动可以挽救宏观模型并解释观测到的异常流量比。我们展示了关于模型灵活性和简并性的重要经验教训。
英文摘要
Flux ratio anomalies in multiply-imaged quasar lenses are a long-standing issue. Using a classical system B1422+231 as a case study, we investigate how typical non-clumpy perturbations beyond elliptical shapes -- multipoles $m_3, m_4$ and radial variations in $q, ϕ_q$ -- can account for the observed image positions and flux ratios under different observational precisions. We extract these perturbations from a pre-selected strong-lensing galaxy sample from the TNG100 simulation. Smooth macroscopic models (SIE+$γ$, EPL+$γ$) are then fitted to the observed image positions alone and to both positions and flux ratios, with and without including the extracted perturbations. With astrometric uncertainty of $σ_{p}=10$ mas, both macro-models alone can already successfully fit image positions within $3σ_{p}$. At $σ_{p}=2$ mas, however, 'astrometric anomalies' appear if smooth macro-models alone are adopted. In this case, adding the extracted perturbations can explain the anomalous image positions. When both positions and flux ratios are adopted, the SIE+$γ$ model family already shows 'flux ratio anomalies' at photometric uncertainty $σ_{f} \le 10\%$ (keeping $σ_{p}=10$ mas). When EPL+$γ$ is used, the smooth model alone can simultaneously fit both positions and flux ratios with $σ_{f}=10\%, 5\%$, but not with $σ_{f}=2\%$, where 'flux ratio anomalies' appear. Adding all four types of extracted perturbations can rescue the macro-models and explain the observed anomalous flux ratios. We present important lessons learned regarding model flexibility and degeneracy.
Comments18 pages, 10 figures, 4 tables, submitted to ApJ. Comments are welcome!
