The Jet Precession In Active Galactic Nuclei

The study of active galactic nuclei (AGN) is one of the most active branches in the field of astrophysics. This thesis gives a investigation on the jet precession of AGN. The single black hole-accretion disk precession model or disk-driven precession model is discussed carefully; Two correlations have been raised and sustained by observational values, which are precession period - absolute magnitude correlation and black hole mass - precession cone semi-angle correlation; A comparison between disk-driven black hole precession and geodetic precession of binary black holes has been performed to check which model plays the leading role in certain circumstances.In the beginning of thematic background, interrelated basic words and fundamental principle are introduced in the first chapter. Finally, physics about precession sorted by precession mechanism are presented curtly.In the second chapter, first, the background, the idea and the formula derivation of the disk-driven precession model are introduced. And some problems on the scale of critical radius and relation with other parameters are discussed aptly. Second, a test with observational values on the disk-driven precession model is done. Then, the impact of black hole masses on disk-driven precession model is discussed. Finally, from two views of observation and theory, the dispersion is analyzed primarily.In the third chapter, precession cone semi-angle is discussed. We found from observational data that there is a correlation between the black hole mass and precession cone semi-angle, we try to explain it theoretically. Then, a simple discussion on solitary precession cone semi-angle follows.In the fourth chapter, different precessions sorted by the models have been summarized. Then, in the view of the precession speed, a comparison is performed between disk-driven precession model and geodetic precession of binary black holes model.In the fifth chapter, first, regarding black hole as solid sphere is doubted. Second, a brief view is given about short period precession.