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The Synchrotron Emission of jets with Transverse Velocity Discrepancy

Chinese Journal of Astronomy and Astrophysics 2004年第4期4卷 311-319页

作者： Hui-QuanLi Jian-ChengWang LiXue NationalAstronomicalObservatories YunnanObservatoryChineseAcademyofSciencesKunming650011 UnitedLaboratoryforOpticalAstronomy ChineseAcademyofSciences GraduateSchooloftheChineseAcademyofSciences

It has been commonly accepted that the bulk velocity of extragalactic jets varies in all directions. We examined the synchrotron radiation of a jet with velocity structure in the direction perpendicular to its axis and found that the spectral energy distribution (SED) is not strongly influenced by this circumstance, that there is only a small increase in the emission intensity and almost no shift in the peak frequency. For objects with smaller inclined angles θ0 between the jet axis and the line of our sight, such as Blazars, the effect is more important. When θ0 exceeds a critical value there is no longer any change in the SED. To compare the bulk speed with different velocity structure, an equivalent speed β is defined which would reproduce the same spectral profile. There possibly exists a stress fμ(y) between layers of the outflow when the velocity is not the same in the jet.

关键词： galaxies: jets radiation mechanisms: non-thermal methods: numerical

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Fermi/LAT observations of lobe-dominant radio galaxy 3C 207 and possible radiation region of γ-rays

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Research in Astronomy and Astrophysics 2018年第6期18卷 93-98页

作者： Sheng-Chu Guo Hai-Ming Zhang Jin Zhang En-Wei Liang Guangxi Key Laboratory for Relativistic Astrophysics Department of Physics Guangxi University Key Laboratory of Space Astronomy and Technology National Astronomical Observatories Chinese Academy of Sciences

3 C 207 is a lobe-dominant radio galaxy with a one sided jet and bright knots, spanning a kpcMpc scale, which have been resolved in the radio, optical and X-ray bands. This target was confirmed as a γ-ray emitter with Fermi/LAT, but it is uncertain whether the γ-ray emission region is the core or knots due to the low spatial resolution of Fermi/LAT. We present an analysis of its Fermi/LAT data acquired during the past 9 years. Different from the radio and optical emission from the core, it is found that theγ-ray emission is steady without detection of flux variation at over a 2σ confidence level. This likely implies that the γ-ray emission is from its knots. We collect the radio, optical and X-ray data of knot-A,the closest knot from the core at 1.4′′, and compile its spectral energy distribution(SED). Although the single-zone synchrotron+SSC+IC/CMB model that assumes knot-A is at rest can reproduce the SED in the radio-optical-X-ray band, the predicted γ-ray flux is lower than the LAT observations and the derived magnetic field strength deviates from the equipartition condition by 3 orders of magnitude. Assuming that knot-A is moving relativistically, its SED from radio to γ-ray bands would be represented well with the single-zone synchrotron+SSC+IC/CMB model under the equipartition condition. These results likely suggest that the γ-ray emission may be from knot-A via the IC/CMB process and the knot should have relativistical motion. The jet power derived from our model parameters is also roughly consistent with the kinetic power estimated with radio data.

关键词： galaxies: active galaxies: jets radiation mechanisms: non-thermal galaxies: individual(3C 207)

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A possible precessing nozzle and the Lense-Thirring effect in blazar 3C 454.3

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Research in Astronomy and Astrophysics 2014年第3期14卷 249-274页

作者： Shan-Jie Qian S.Britzen A.Witzel T.P.Krichbaum Heng-Qian Gan Long Gao National Astronomical Observatories Chinese Academy of Sciences Max-Planck Institt fr Radioastronomie

The kinematics of superluminal components in blazar 3C 454.3 are *** components are included： superluminal knots R1, R2, R3, R4, A, B, C and D（from Britzen et al. 2013） and C4 （from Pauliny-Toth 1998）. We find that their kine-matics derived from VLBI observations can be consistently interpreted in terms of ajet precession scenario with a period of about 14.5 yr. We discuss the model fits oftheir trajectory, distance from the core and apparent velocity. We show that the bulkLorentz factor （in the range 4 to 15） derived for these components does not have anydependence on the phase of the precession （or position angle for ejection）. The Lense-Thirring effect is assumed to interpret the precession of the jet nozzle. The resultsobtained for blazar 3C 454.3 are only suggestive. They are not unique and have yet tobe tested, but they might be useful for understanding the kinematics of superluminalcomponents in blazars and for disentangling different mechanisms and factors.

关键词： radio continuum: galaxies galaxies: jets galaxies: kinematics galaxies: individual (blazar 3C 454.3)

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