High Energy Gamma-ray Agns, The Radio Observations And Research

Energetic Gamma Ray Experiment Telescope (EGRET) in space and Whip-ple γ-ray telescope on the ground have detected more than 80 AGNs on γ-rayband at energies above 100 MeV. They are all radio-loud sources, and classi?edas blazars. The γ-ray ?are is usually accompanied by the radio ?are. The frac-tion with superluminal motion of radio jet is rather high. Since all γ-ray AGNshave strong radio emission, the relationship between γ-ray and radio emission isworthy to study. As the modern astronomical observational technique with the highest resolu-tion, VLBI can provide key contribution to the study of relativistic jets structure,superluminal motion and bending jet of γ-ray AGNs. It is helpful to discover therelationship between γ-ray and radio emission of them. The purpose of this thesis is to complete the sample of radio images of γ-rayAGNs. We use VLBI to observe some γ-ray AGNs without radio images, get theircompact structure, and study their morphology structure and emission property. In Chapter 1, the basic properties of AGNs are introduced. 87 AGNs withhigh-energy emission were collected for research. In Chapter 2, we present the radio observations of a sub-sample of γ-rayAGNs. Radio images of 13 γ-ray AGNs observed by European VLBI Network(EVN) are given. The VLBI structures of 1604+159 and 2022?077 are reportedfor the ?rst time. The observed results show that most of these sources are re-solved with core-jet structure on the mas scale, except two are too compact to beresolved. Compared with the previous EVN VLBI images, we detect the super-luminal motion in 0827+243, 0829+046 and 1604+159. Their apparent velocitiesare 18.5, 6.9, 2.2–3.5 c, respectively. 1604+159 is identi?ed as superluminal sourcefor the ?rst time. Meanwhile, we investigate the bending jet of the sample frommas scale to arcsec scale. In Chapter 3, we present the results of the VLBI observations at 1.67, 5 and15 GHz and MERLIN observations at 5 GHz for γ-ray quasar 0202+149. Theresults ?rst reveal that the source contains two mini-lobes located on both sides 第xi页Abstractof a bright radio core on subarcsecond scales. The main mini-lobe is brighter andfarer from the core than the other one. We found that the jet is strong bent onmas scale. This means the jet in 0202+149 maybe follows a helical path on acone. According to the subarcsecond structures, 0202+149 is easily to be thoughtas a compact symmetric object (CSO). But based on the facts of the superluminalmotion, the variability of ?ux density and bending jet, we don't think that thesource 0202+149 is a CSO. In Chapter 4, four epoch VLBI observations and the model-?tting results ofDA193 are presented. We detect a proper motion of 0.105 ± 0.02 masyr? of 1the jet component, which corresponds to an apparent velocity of 4.5 ± 0.86 c.According to the Doppler factor and of the brightness temperature, this sourceis considerably boosted towards the line of sight. The velocity is about 4 timeslarger than previous estimation, which may indicate (1) that the jet componentis being accelerated, possibly due to a bending jet aligned close to the line ofsight; or (2) that there are two di?erent components ejected in two ?ares. In thisChapter, we also present the results of the VLBI observations at 5 and 8.4 GHz ofthe compact symmetric object (CSO) OQ208. We ?nd that the expansion speedbecome slow, which maybe due to the shocked ambient medium on the front. Atthe same time, we ?nd that the hot-spots component near core is more free-freeabsorbed at low frequency. The reason is that the electron density is larger nearlyin the nuclear region than in outer region. In Chapter 5, we analysis the position angle (?PA) between mas scale andarcsecond scale. On the basis of the sample given by Hong, we expand the samplewith our observational results. Our statistical results support those of Hong, i.e.γ-ray quasars have small ?...