高红移 blazar 的宇宙学距离测量：OJ 248（z=0.939）与 4C +38.41（z=1.814）
Cosmological Distance Measurements of High Redshift Blazars: OJ 248 (z=0.939) and 4C +38.41 (z=1.814)
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中文总结 AI 辅助
本研究用43 GHz射电光变曲线，在两种T_B,int假设下估算高红移blazar OJ 248和4C +38.41的角直径距离，发现系统不确定性影响结果可靠性，指出AGN变异性测距法需进一步改进。
中文摘要 AI 辅助
本研究利用43 GHz射电光变曲线，估算了两个高红移活动星系核（AGN）OJ 248（z=0.939）和4C +38.41（z=1.814）的角直径距离，旨在将基于AGN变异性的距离测量方法拓展至高红移区域。在两种本征最大亮温度T_B,int假设下对距离估算结果进行分析：（1） equipartition温度；（2）样本平均T_B,int。作为代表性结果，采用equipartition温度时，OJ 248和4C +38.41的角直径距离分别估算为7592.7 ± 396.7 Mpc和11069.8 ± 1216.9 Mpc。此外，利用逆康普顿法计算多普勒因子，并基于该值获得额外的距离估算结果。误差预算分析显示，最显著的系统不确定性源于历元选择。这些结果表明，系统效应对推导的距离估算值有重大影响，尤其在高红移区域会限制其可靠性。降低这些不确定性需要改进观测 cadence 并降低拟合后噪声。AGN变异性为距离估算提供了一种替代方法，但本研究结果揭示了当前方法学存在的显著局限性，表明在能够可靠评估其宇宙学适用性之前，需要进一步的方法学和观测改进。
英文摘要
In this study, we estimated the angular diameter distances to two high-redshift active galactic nuclei (AGNs), OJ 248 (z = 0.939) and 4C +38.41 (z = 1.814), using 43 GHz radio light curves. The aim of this work is to extend AGN variability-based distance measurement methods to the high-redshift regime. The distance estimates were analyzed under two assumptions for the maximum intrinsic brightness temperature TB,int: (1) the equipartition temperature, and (2) the sample-averaged TB,int. As a representative result, when adopting the equipartition temperature, the angular diameter distances to OJ 248 and 4C +38.41 are estimated to be 7592.7 +/- 396.7 Mpc and 11069.8 +/- 1216.9 Mpc, respectively. In addition, Doppler factors were calculated using the inverse-Compton method, and additional distance estimates were obtained based on these values. Our error budget analysis shows that the most significant systematic uncertainty arises from epoch selection. These results indicate that systematic effects have a substantial impact on the derived distance estimates and limit their reliability, particularly in the high-redshift regime. Reducing these uncertainties will require improved observational cadence and reduced post-fit noise. AGN variability provides an alternative approach to distance estimation. However, our results reveal significant limitations in the current methodology and indicate that further methodological and observational improvements are required before its cosmological applicability can be reliably assessed.
