Study On Jet And Accretion Characteristics Of Fermi Blazars

As one of the most intense subclasses of active galactic nuclei,blazars usually have the phenomena of high luminosity and high polarization.Their radiation is dominated by relativistic jets,which are usually thought to be directed at the observer on Earth.As a class of objects which have been proved to be the sources of most extragalactic GeV-TeV radiation,blazars are the main targets for studying the cosmic ?-ray background,the intergalactic magnetic field,and the contribution to the extragalactic background radiation.Their broad-band energy spectrum distribution(SED)is usually bimodal,which is well explained by synchrotron radiation and inverse Compton scattering of relativistic electrons in jets.According to the characteristics of their emission lines,they can be divided into Flat Spectrum Radio Quasars(FSRQs)and BL Lacs objects(BL Lacs).This classification method is simple,but not precise,the research on the difference and connection between the physical properties of the two subclass has always been the forefront topic in the field of blazars.In this paper,we study the correlation between some observation parameters and physical parameters of the FSRQs and BL Lacs,and try to explain the difference between the two from the physical nature.This paper is divided into five chapters:Chapter 1 is a brief introduction to active galactic nuclei,including their basic characteristics,classification based on observed features,and the most widely accepted models.In chapter 2,we introduce the blazars,including its observation characteristics,SED characteristics,optical variability characteristics,and discuss the "blazars sequence".In chapter 3,we focus on the mechanisms of blazars radiation,including blackbody radiation,synchrotron radiation and inverse Compton scattering,as well as lepton and hadronic models for explaining bimodal structures.Chapter 4 and Chapter 5 are our research content,in chapter 4 We collected data of 442 blazars from the literature,including 215 FSRQs and 227 BL Lacs,to investigate the correlation between j et power and multi-wave luminosity.The results are as follows:(1)for FSRQ,jet power is strongly correlated with the luminosity of radio,optical band,X-ray and gamma rays.And the order of luminosity distribution is:log L_?>logL_O>logL_X>logL_R.(2)For BL Lac,jet power is strongly correlated with the luminosity of radio,optical bands and gamma-rays.But there is only a weak correlation between jet power and Xray luminosity.And the order of luminosity distribution is:log L_O>logL_?>logL_X>logL_R.Moreover,the luminosity of each band of BL Lac is less than that of FSRQs.We believe that these differences are due to differences in the intrinsic properties of FSRQ and BL Lac,mainly due to differences in accretion modes and jet radiation mechanisms,etc.In Chapter 5,we further collected the black hole mass,accretion disk luminosity and optical to y ray broadband spectral index of 94 BL Lacs and 184 FSRQs,then calculated the Eddington luminosity according to the black hole mass,and further calculated the Eddington ratio.By studying the correlation between them,we found that:(1)The redshift and Eddington ratio of FSRQs both larger than that of BL Lacs on the whole.(2)BL Lacs showed a strong positive correlation between the optical to y ray broadband spectral index ?_O? and Eddington ratio L_Disk/L_Edd,while FSRQs had almost no correlation.(3)The jet power P_jet of FSRQs has a strong positive correlation with the black hole mass M_BH,but only a weak positive correlation with the Eddington ratio L_Disk/L_Edd.On the contrary,the jet power P_jet of BL Lacs has a weak negative correlation with the black hole mass M_BH,but a strong positive correlation with the Eddington ratio L_Disk/L_Edd.These differences all reflect the accretion mode,j et formation mechanism and other intrinsic physical properties between them are very different,and there may be an evolutionary relationship between them.