发表机构
Konkoly Observatory, HUN-REN Research Centre for Astronomy and Earth Sciences; ELTE Eötvös Loránd University; Institute of Astronomy, Faculty of Physics, Astronomy and Informatics, NCU; Joint Institute for VLBI ERIC; Shangqiu Normal University; University of Science and Technology of China（孔科利天文台，HUN-REN 地球与天文学研究中心; 布达佩斯罗兰大学; 托伦大学物理、天文与信息学院天体物理研究所; 甚长基线干涉测量联合研究所; 商丘师范学院; 中国科学技术大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
研究红移z>4的三个射电类星体射电形态，分析多源多频率干涉数据及存档观测，发现两个类星体有复杂结构似法纳罗夫 - 莱利II型射电星系，第三个有单侧结构，还明确了致密射电特征与AGN中心或热点的关系。
AI 中文摘要
高红移类星体在研究超大质量黑洞和活动星系核（AGN）的生长与演化中起着至关重要的作用。射电噪类星体还能让我们研究喷流与其环境之间的相互作用。我们旨在揭示三个红移z>4的射电类星体的射电形态，它们根据之前的甚长基线干涉测量（VLBI）观测包含毫角秒（mas）尺度的致密射电特征，但在角秒尺度显示出显著的通量密度，表明存在无法通过最高分辨率观测采样的延展射电结构。我们分析了在各种角分辨率和多个频率下获得的射电干涉测量数据，包括国际低频阵列和增强型多元素远程链接干涉仪网络的观测。我们还对目标的欧洲VLBI网络存档观测进行了重新成像。两个类星体（J0813+3508和J1231+3816）呈现出具有热点的复杂射电结构，延伸到数十千秒差距。它们类似于具有极弯曲喷流形态的法纳罗夫 - 莱利II型射电星系。第三个天体（J1548+3335）显示出尺寸约为10千秒差距的单侧结构。在其之前的mas尺度分辨率射电观测中没有相对论性增强的迹象。其从较低分辨率观测得出的射电功率和（推断的）线性尺寸与已知的高功率致密陡谱源相似。我们发现先前检测到的mas尺度致密射电特征与AGN的中心有关，或者在一种情况下与延展瓣中的一个热点有关。
英文摘要
High-redshift quasars play an essential role in studying the growth and evolution of supermassive black holes and active galactic nuclei (AGN). Radio-loud quasars additionally enable us to investigate the interactions between the jets and their environment. We aimed to reveal the radio morphology of three radio quasars at redshifts z>4 that contain milliarcsecond (mas) scale compact radio features according to previous very long baseline interferometry (VLBI) observations, but show significant flux density at arcsecond scales, indicating the presence of extended radio structure that cannot be sampled by the highest-resolution observations. We analysed radio interferometric data obtained at various angular resolutions and multiple frequencies, including observations made by the international Low-Frequency Array and the enhanced Multi-Element Remotely-Linked Interferometer Network. We also re-imaged archival European VLBI Network observations of our targets. Two quasars (J0813+3508 and J1231+3816) exhibit complex radio structures with hotspots, extended to tens of kpc. They resemble Fanaroff--Riley II-type radio galaxies with extremely bent jet morphology. The third object (J1548+3335) shows a one-sided structure of $\lesssim 10$ kpc size. There was no sign of relativistic boosting at its previous mas-scale resolution radio observations. Its radio power and (inferred) linear size derived from the lower-resolution observations are similar to the known high-power compact steep-spectrum sources. We found that the previously detected mas-scale compact radio features are related to the centres of the AGN or in one case to one of the hotspots in an extended lobe.
Comments17 pages, 11 figures, accepted for publication in Astronomy and Astrophysics, affiliation is corrected
