大样本“变脸”活动星系核多频射电巡天观测结果的统计研究  

A Statistical Study of A Large Sample of Changing-look Active Galactic Nuclei with Multi-frequency Radio Sky Surveys

作　　者：吴烨 杨军 孙晓辉 WU Ye;YANG Jun;SUN Xiao-hui(School of Physics and Astronomy,Yunnan University,Kunming 650500;Department of Space,Earth and Environment,Chalmers University of Technology,Onsala Space Observatory,SE-43992 Onsala)

机构地区：[1]云南大学物理与天文学院,昆明650500 [2]Department of Space,Earth and Environment,Chalmers University of Technology,Onsala Space Observatory,SE-43992 Onsala

出　　处：《天文学报》2023年第1期51-69,共19页Acta Astronomica Sinica

基　　金：国家自然科学基金项目(11763008)资助。

摘　　要：光学波段的“变脸”AGN (changing-look Active Galactic Nucleus, CL AGN)是光谱类型发生变化AGN的统称.近年来,越来越多观测证据表明这类现象与中央超大质量黑洞吸积活动有关.而黑洞吸积率的变化可能会引起喷流的增强或者减弱,进而导致射电波段观测性质的变化.在已发表的文献中,收集了74个光学波段证认的“变脸”AGN、90个“变脸”AGN的候选体.基于这个目前最大并且选源方式多样化的非完备样本,探讨了“变脸”AGN在射电波段的观测性质.从澳大利亚平方公里阵先导设备(Australian Square Kilometre Array (SKA) Pathfinder, ASKAP)和美国甚大阵甚大阵(Very Large Array, VLA)的4大射电巡天观测中,发现了51个“变脸”AGN (含21个候选体)在0.9–3 GHz存在射电波段的对应体,样本的射电探测率约为41%,与一般AGN的射电探测率无显著区别.此外,分析了这些源的射电谱指数,发现在1.4 GHz和3 GHz频段“变脸”AGN相对于一般射电源有较平的射电谱.该统计结果或可解释为“变脸”AGN存在一些较年轻并且在毫角秒尺度上结构致密的射电喷流活动.Optically changing-look active galactic nuclei(AGNs) are a class of objects that exhibit appearance or disappearance of broad lines. Recent studies have shown that these changing-look activities very likely result from the accretion activities of the central supermassive black holes. Large variation of the accretion rate might cause jet ejection and fading events, thus lead to a certain variability of observational radio properties. From the published literature, 74 changing-look AGNs and 90 changing-look AGN candidates identified in optical observations were collected. Based on this largest, complex and incomplete sample to date, the radio properties of changing-look AGNs were investigated. The radio counterparts of 51 changing-look AGNs(including 21 candidates) were discovered from the all-sky surveys conducted by the Australian Square Kilometre Array Pathfinder(ASKAP) and Very Large Array(VLA)covering the frequency range of 0.9–3 GHz. This corresponds to a detection rate of about 41 percent,which is similar to general AGNs. The radio spectral indices between 0.9 and 1.4 GHz, and between 1.4 and 3 GHz were calculated, which suggest that these changing-look AGNs tend to have atter radio spectra than normal AGNs. This statistical result indicates that changing-look AGNs might host some young, compact, and faint radio jets.

关 键 词：星系:活动 星系:喷流 星系:赛弗特 星系:统计 射电连续谱:星系 

分 类 号：P158[天文地球—天文学]