Multiwave-length Analysis Of Large Scale Jets In Fanaroff-Riley TypeI Radio Galaxies

Jets commonly exist in the active galactic nuclei, especially in radio galaxies and QSOs. It is highly collimation and high-speed material outflow from galactic nucleus. It is an important passway for transporting material, energy and magnetic field from the core to the radio-lobes or hotspots. Its high speed (close to the velocity of light) suggests the presence of deep potential well at nuclei. Since the first jet found in 1918, the study of jet has become one of the focuses of current astrophysics. The VLA and the VLBI equipment developed in 1970's have made detailed study of radio jet structive possible. The satellite Chandra and XMM-NEWTON had gradually opened the jet in the high energy wave-band mystical veil, taking people to the new field of jet research at high energy waveband. Optics jets have been extremely rare, so far the number discovered is very few. However, studies of the spectrum energy distribution of the jets are very important for us to understand jet physics as well as to study the characteristics of AGN central engine, etc. This thesis analyzes the multi-wave band energy spectra of jets in FR-I radio galaxies, and to study the whole kinematics behavior of jets. By modelling the spectra of individual knots physically, some good results are presented. The dissertation is divided into five chapters.In the first chapter, I outline the importance of jet research and briefly described the relativistic beaming model of the jet. We discussed the superluminal motion phenomenon and the Doppler beaming effect and the rapid variability phenomenon. In the context of the beaming model, I briefly reviewed major radiative processes in the jet, including synchrotron radiation and inverse compton scattering. The similarities and differences between the processes are discussed. In chapter two, based on the radiation model of spectral energy distribution (SED) of the jet, I analyzed the SED of the large scale jet in nearby FR-I radio galaxy M87 for its rich data.. Doppler factor of the different knots in M87 jet are obtained by modelling their SED. The result suggests that M87 has a moderate relativistic jet, viewed at an inclination of 20 to 30 degree. Moreover the jet decelerates gradually from inner knots to outer knots, at the same time the viewing angle of different knots in the jet varies.Next, we attempt to build a large scale jet sample of FR-I radio galaxies, to check whether the kinematics of the jet in M87 is common behavior for FR-I radio galaxies or not. We compile a sample of 11 Fanaroff—Riley type I Radio Galaxies (FR-I RGs) with multi-wavelength observations to address the dynamic behavior of the jets in these objects. Optical images acquired by the Hubble Space Telescope (HST) are carefully analyzed. The method and reduction procedure are described in detail. Unresolved optical cores emerge in 8 FR-I RGs after properly removal of starlight from the host galaxies, out of which 5 are identified for the first time. Broad band spectral properties of these newly identified compact cores are compared with that previously found in FR-I RGs, as well as that of low-energy-peaked BL Lac objects. The similarity between them argus for the same non-thermal synchrotron origin. Well-resolved optical jets with knotty morphologies are found in three FR-I RGs in our sample, namely 3C15, 3C66B and B2 0755+37. The optical counterparts to the inner radio/X-ray jets are identified and a clear one-to-one correspondence between the optical, radio and X-ray knots is found. The structure and information about the optical jets are discussed. Physical parameters such as the knots position, flux and size are also presented.In the fourth chapter, we analyze the spectrum energy distribution of jets obtained in the last chapter, applying synchrotron model similar to the one for M87, we drived the Doppler factor of the jet different knots component. We find that in the FR-I radio galaxies, the large scale jets indeed display decelerated kinematics behavior. I found also an extremely well correlated between the radio emission and optical emission of the core, indicating that the optical emission of the core is originates from the synchrotron radiation mechanism as the radio emission. The similarity of the spectrum of core and jet is also in favour of this suggestion.The last chapter briefly presents the future work.