发表机构
Lebedev Physical Institute of the Russian Academy of Sciences; Harvard University; Crimean Astrophysical Observatory; Max-Planck-Institut für Radioastronomie（俄罗斯科学院列别捷夫物理研究所; 哈佛大学; 克里米亚天体物理观测站; 马克斯·普朗克射电天文研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文利用地面VLBI数据对1074个活动星系核进行首次系统性折射散射子结构搜索，发现9个源符合预期，多数位于天鹅座强散射区，证明该效应罕见但可作星际介质探针。
AI 中文摘要
我们展示了首次利用地面甚长基线干涉测量（VLBI）数据对活动星系核（AGN）中的折射散射子结构进行系统性搜索的结果。我们选取了1074个角尺寸表现出陡峭频率依赖性的活动星系核，并将观测到的长基线可见度振幅与散射展宽图像的折射子结构模型预测进行了比较。有九个源显示出与预期折射噪声水平的一致性，其中包括类星体TXS 2005+403（J2007+4029），这证实了先前针对该源报道的结果。值得注意的是，这些活动星系核中的大多数位于天鹅座区域——这是银河系强散射的关键“热点”之一。对于五个选定的活动星系核，我们确定了至少两个数据质量足够高且具有长基线探测的历元，表明存在散射子结构。我们证明了活动星系核中的折射散射子结构是一种罕见效应，需要高灵敏度、足够的源亮度以及星际介质中湍流特别强的视线方向。尽管如此，活动星系核可以作为探测湍流星际介质的强大探针。我们讨论了提高VLBI观测灵敏度的策略，并确定了在未来观测中可靠探测和研究折射子结构最有前景的源。
英文摘要
We present the results of the first systematic search for refractive scattering substructure in active galactic nuclei (AGN) using ground-based very long baseline interferometry (VLBI) data. We selected 1074 AGNs showing a steep frequency dependence of their angular sizes and compared the observed long-baseline visibility amplitudes with the predictions of the refractive substructure model for scatter-broadened images. Nine sources showed consistency with the expected level of refractive noise, including the quasar TXS 2005+403 (J2007+4029), which confirms previously reported results for this source. Remarkably, the majority of these AGNs are located in the Cygnus region -- one of the key ``hotspots'' of strong Galactic scattering. For five selected AGNs, we identified at least two epochs with sufficiently high data quality showing long-baseline detections, suggesting the presence of scattering substructure. We showed that refractive scattering substructure in AGN is a rare effect, requiring high sensitivity, sufficient source brightness, and lines of sight with particularly strong turbulence in the interstellar medium. Nevertheless, AGNs can serve as powerful probes of the turbulent interstellar medium. We discuss strategies for improving the sensitivity of VLBI observations and identify the most promising sources for reliable detection and investigation of refractive substructure in future observations.
Comments11 pages, 6 figures, 3 tables; Submitted to MNRAS
