Multi-waveband Electromagnetic Radiation And High-energy Neutrino Radiation Of Blazars

Blazars are the most extreme form of active galactic nuclei(AGNs),with their jets pointing in the direction of the observer.At the same time,being some of the most powerful persistent sources of electromagnetic radiation in the universe,blazars have been widely considered as candidate sources for high-energy cosmic rays and neutrinos.With the advent of high-quality observation data detected by space and ground-based telescopes,our understanding about radiation mechanisms of the relativistic particles in the jet is promoted.In this thesis,we develop the leptonic and leptohadronic modes based on observation phenomena,and study the multi-waveband radiation properties,jet power and high-energy neutrino emission.In the first chapter of this thesis,we briefly introduce the multi-messenger observations of blazar jet,then summarize the radiation processes in detail,and finally summarize three commonly used jet models,which are one-zone model,spine-layer model and standard Blandford-K?nigl model.In Chapter 2,we study the requirement of the jet power in the conventional p?models for Te V BL Lac objects.We select a sample of Te V BL Lac objects whose spectral energy distributions are difficult to explain by the one-zone leptonic model.Based on the relation between the p? interaction efficiency and the opacity of ?? absorption,we study the requirement of the jet power in the conventional p? models for Te V BL Lac objects.For most Te V BL Lacs in our sample,we find that the obtained minimum jet powers exceed the Eddington luminosity of the supermassive black holes.Implications for the accretion mode of the SMBHs in these BL Lac objects and the origin of their Te V emissions are discussed.We suggest that the leptonic origin with more complicated topology of the radiation zone and the hadronuclear interaction should be considered.In Chapter 3,we show that the high-energy neutrino event Ice Cube 170922 A can be interpreted by the inelastic hadronuclear interactions between the accelerated cosmic-ray protons in the relativistic jet and the dense gas clouds in the vicinity of the SMBH.Such a scenario only requires a moderate proton power in the jet,which could be much smaller than that required in the conventional hadronic model which instead calls upon the photomeson process.Meanwhile,the flux of the multiwavelength flare from the optical to gamma-ray band can be well explained by invoking a second radiation zone in the jet at a larger distance to the SMBH.In our model,the neutrino emission lasts a shorter time than the multiwavelength flare,so the neutrino event is not necessarily correlated with the flare,but it is probably accompanied by a spectrum hardening above a few Ge V.In Chapter 4,we further discuss the difficulties of the conventional one-zone p?model in interpreting the coincidence between Ice Cube 170922 A and a multiwavelength flare from TXS 0506+056.It has been shown with standard one-zone models that neutrinos can be produced in the blazar jet via hadronic interactions,but with a flux that is mostly limited by the X-ray data.In this work,we explore the neutrino production from TXS 0506+056 by invoking two physically distinct emission zones in the jet,with an inner blob inside of or close to the broad-line region(BLR)and an outer one well beyond the BLR.Using the Doppler-boosted radiation of the BLR as the target photon field,the inner zone accounts for the neutrino and gamma-ray emission via p? interactions and inverse Compton scattering,respectively,while the outer zone produces the optical and X-ray emission via synchrotron and synchrotron selfCompton processes.The different conditions of the two zones allow us to suppress the X-ray emission from the electromagnetic cascade,and set a much higher upper limit on the muon neutrino flux than in one-zone models.We compare our scenario in detail with one-zone models discussed in the literature,and argue that differentiating between such scenarios will become possible with next-generation neutrino telescopes,such as Ice Cube-Gen2.In Chapter 5,we briefly introduce the Very Long Baseline Array observations of M 87 jet.Based on this,We develop a self-consistent multi-zone model to simulate the time-dependent multi-waveband emission and light curves from blazars.Based on Very Long Baseline Array observations of M 87 jet,we assume that there are hundreds of thousands of emission zones in the jet.In the model,the relativistic electrons in each emission zone are evolved taking into account the the synchrotron,inverse-Compton and adiabatic losses.We apply this model to study some observations that difficult to be explained by the conventional one-zone models,which are the flat radio spectra,Gaia-VLBI downstream offset,and the Doppler-factor crisis.