Radio core dominance of Fermi/LAT-detected AGNs  

作　　者：ZhiYuan Pei JunHui Fan Denis Bastieri JiangHe Yang HuBing Xiao 

机构地区：[1]Diparimento di Fisica e Astronomia“G.Galilei”.Universita di Padova,Padova 1-35131,Italy [2]Istituto Nazionale di Fisica Nucleare,Sezione di Padova,Padova 1-35131,Italy [3]Center for Astrophysics,Guangzhou University,Guangzhou 510006,China [4]Astronomy Science and Technology Research Laboratory of Department of Education of Guangdong Province,Guangzhou 510006,China [5]Department of Physics and Electronics Science,Hunan University of Arts and Science,Changde 415000,China

出　　处：《Science China(Physics,Mechanics & Astronomy)》2020年第5期105-123,共19页中国科学：物理学、力学、天文学（英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.11733001,and U1531245);the Natural Science Foundation of Guangdong Province(Grant No.2017A030313011)。

摘　　要：We present a sample of 4388 AGNs with available radio core-dominance parameters—defined as the ratio of the core flux densities to the extended ones, R = S_(core)/S_(ext).—which includes 630 Fermi-detected AGNs from the fourth source catalog(4FGL) of the Fermi Large Area Telescope(Fermi/LAT);the rest are non-Fermi-detected AGNs. In our sample, 584 blazars are Fermi-detected and 1310 are not. The sample also contains other subclasses, such as Seyferts, Fanaroff-Riley I/II galaxies, and normal galaxies.We investigate various properties of the Fermi-detected and non-Fermi-detected AGNs by using core-dominance parameters,capitalizing on a previous study which showed that R is a good indicator of beaming. We then calculate radio spectral indices for the whole sample, and adopt γ-ray-photon indices for the Fermi AGNs from the 4FGL catalog to discuss the properties of different subclasses. We obtain a relation between the core-dominance parameters and the radio spectral indices for both Fermi and non-Fermi sources, assuming a two-component model in the radio band. Our previous study ruled out the assumption that the core-dominance parameters and radio spectral indices are quite different for different AGN subclasses. This holds not only for Fermi sources but also for non-Fermi sources. In particular, R is, on average, greater for the former AGNs than for the latter.In this study, we enlarge our sample with available values of R to 4388 AGNs, and the obtained conclusions are consistent with our previous study. We assume that the same two-component model holds for the γ-ray band as for the radio band, and therefore,adopt the same relation between the core-dominance parameters and the γ-ray-photon indices for Fermi AGNs. Our fitting results indicate that the γ-ray emissions of Fermi blazars originate mainly from the jet, and therefore, we conclude that the Fermi blazars are beamed.We present a sample of 4388 AGNs with available radio core-dominance parameters—defined as the ratio of the core flux densities to the extended ones, R = Score/Sext.—which includes 630 Fermi-detected AGNs from the fourth source catalog（4FGL） of the Fermi Large Area Telescope（Fermi/LAT）; the rest are non-Fermi-detected AGNs. In our sample, 584 blazars are Fermi-detected and 1310 are not. The sample also contains other subclasses, such as Seyferts, Fanaroff-Riley I/II galaxies, and normal galaxies.We investigate various properties of the Fermi-detected and non-Fermi-detected AGNs by using core-dominance parameters,capitalizing on a previous study which showed that R is a good indicator of beaming. We then calculate radio spectral indices for the whole sample, and adopt γ-ray-photon indices for the Fermi AGNs from the 4FGL catalog to discuss the properties of different subclasses. We obtain a relation between the core-dominance parameters and the radio spectral indices for both Fermi and non-Fermi sources, assuming a two-component model in the radio band. Our previous study ruled out the assumption that the core-dominance parameters and radio spectral indices are quite different for different AGN subclasses. This holds not only for Fermi sources but also for non-Fermi sources. In particular, R is, on average, greater for the former AGNs than for the latter.In this study, we enlarge our sample with available values of R to 4388 AGNs, and the obtained conclusions are consistent with our previous study. We assume that the same two-component model holds for the γ-ray band as for the radio band, and therefore,adopt the same relation between the core-dominance parameters and the γ-ray-photon indices for Fermi AGNs. Our fitting results indicate that the γ-ray emissions of Fermi blazars originate mainly from the jet, and therefore, we conclude that the Fermi blazars are beamed.

关 键 词：active GALACTIC nuclei(AGNs) QUASARS γ-rays 

分 类 号：TN925[电子电信—通信与信息系统]