The Study On The Accretion And Jet Physcis For M87

The low-luminosity active galactic nuclear(LLAGN)-M87 is a very famous active galactic nuclear,due to its very huge black-hole mass and its proximity.Compared to our own galaxy Sgr A*,the jet in M87 has been clearly observed.The studies on BH accretion and jet have made big progress in last several tens years.However,there are still many important issues that are very unclear.For example,the evolution and transition of accretion process,the jet formation,jet acceleration,jet collimation and compositions etc.In this paper,we explored the possible accretion and jet process through studying the LLAGN-M87.In chapter 1,we briefly introduced some basic physical characteristics and classification of the BH(e.g.,stellar-mass BH,intermediate-mass BH and supermassive BH).Then we reviewed the basic features and recent progress of active galactic nuclei(AGNs),where the AGN observation,classification,unification,and possible intrinsic physics are introduced.Furthermore we introduced the LLAGN as a special class of AGN.Then,the LLAGN-M87 is specially introduced,which is the source we focused in this thesis.In the last,we briefly presented the accretion process and jet physics,which include the different accretion models(especially for advection dominated accretion flow,ADAF),jet formation,jet collimation and compositions etc.In chapter 2,we mainly investigated the accretion and jet process near the black-hole horizion of M87 through the high-spatial resolution,multi-waveband data and Faraday rotation measure(RM).Recently,Prieto et al.presented the multi-waveband spectral energy distribution(SED)of M87.We found that there is a bump in the millimeter waveband as observed by the Atacama Large Millimeter/submillimeter Array(ALMA).Further more,the spectral index at low-frequency radio band(Sv ? v-k,k?0.2)is also different from high-frequency radio band(k?0.3).These features are quite similar to those of Sgr A*(the supermassive BH in our galaxy).And we find that the SED is difficult to fit with pure ADAF or pure jet model.Similar to Yuan et al.2003,we used a coupled ADAF-jet model to fit the SED of M87.We found that the millimeter bump can be naturally reproduced by the synchrotron emission from the thermal electrons in ADAF,and the low-frequency radio emission and X-ray emission may predominantly come from the synchrotron radiation of non-thermal electrons in the jet.We also found that the millimeter radiation predominantly comes from the region within 10Rg of ADAF,which is roughly consistent with the recent very long baseline interferometry(VLBI)observations at 230 GHz.By fitting the millimeter and sub-millimeter waveband observations,the electron number density in ADAF is ne ? ?-1,which is roughly consistent with that determined from X-ray observation near the Bondi radius and recent numerical simulations.Finally,according to the RM obtained by the polarization observation,we considered the possible location of the polarizing source(from the different positions in the accretion disk or jet)and found that the calculated RM in the accretion disk is roughly consistent with the observational constraints.Due to the complexity of jet physics,we can not completely exclude the possibility of RM is from the jet.In chapter 3,we studied the BH spin of M87.We firstly introduced some methods for measuring the BH spin,which include continuum-fitting,broadened Fe Ka line analysis,high frequency quasi-periodic oscillation,X-ray polarization,jet formation model,accretion disk and jet precession and so on.The jet formation may be related to the accretion process.The black-hole spin and accretion rate can be constrained from the observation spectrum and the jet power based on the coupled ADAF-jet model.And here we use a hybrid model which combined BZ and BP to calculate the jet power self-consistently.We found that the BH in M87 should be fast rotating,the BH dimensionless spin parameter should be a*? 0.96,even consider the uncertainty of some model parameters.In chapter 4,we gave a brief summary about this thesis,and also disscussed the possible directions for our future work.