The Study Of Age On The Large Scale Radio Relic Of Active Galactic Nucleus M87

M87 is the active galactic nucleus(AGN)that very close to us.The"image"of black hole around the core of M87 given by the Event Horizon Telescope has attracted wide attention.The relativistic jet of M87 extends about 2kpc from its central black hole outward,and in the region larger or much larger than 2kpc,appears large-scale radio relics surrounding the hot core.It is generally believed that the radio relic is produced by the interaction between the jet and the surrounding interstellar medium.While,detailed mechanism of jet origin and jet-matter interaction are still open questions.The study of the age of the radio relic around M87 not only helps us to understand the morphology formation of AGNs,but also enables us to have indepth investigation on the physics of black hole,accretion disk and jet,as well as the AGN feed back to the host galaxy.AGN M87 characterized by its large mass and short distance to us.The rich multi-band observations of it resemble the sun providing a natural laboratory on the investigation of stars.As for the study of age of radio relics of M87,a lot of works have been done in the past,focusing on the estimation of the average age in some large scale.Whereas,the age in the 5kpc scale around M87 has not be seen in literature.In this thesis,the radio data of M87is reanalyzed,and age of the 5kpc scale around M87 is investigated in detail by the broadband energy spectrum analysis tool BRATS,which gives the age of each region pixel by pixel for the first time.In the first chapter of this thesis,different types of AGNs are introduced,and more detailed description is given on the composition of radio galaxies,radiation mechanisms,and the surrounding environment.Furthermore,several models of spectral ageing are introduced.The second chapter studies the age of the radio relics around AGN M87,which contains following steps.First of all,the observational data of VLA from 2013 to 2014,covering the frequency of S(2-4GHz)band are analyzed.The composite images are obtained through different array configurations,and the images of different frequency windows are mapped,on which spectral ageing analysis can be performed.Finally,using images of different frequencies,a detailed spectral ageing analysis on M87 using the program package(BRATS)developed by Jeremy Harwood in 2013 is conducted.Different spectral ageing models are adopted in obtaining the spectral ages of different regions of radio relics around M87.The third chapter further discusses the results of the data processing.First of all,the spectral age of radio relics around M87 are obtained by using different spectral ageing models.The maximum fitting ages of radio relics as a whole can be obtained by KP,JP and Tribble models under a magnetic field of 5.5n T which are respectively2.11_-0⁺⁰..₄7₉3Myr?2.34_-0⁺⁰..₃3₂6Myr?2.70_-0⁺⁰..₄4₃4Myr.Secondly,the maximum fitting age of the right radio lobe and the left one are 1.89Myr and 2.34Myr repectively.The result of age fitting shows that the left radio lobe is increasing from top to bottom,which is inconsistent with the scenario of the precession of a single jet from left to the right.In fact,it favors that the left and right radio lobe are generated by a bipolar jet respectively.Finally,as the Tribble model with a assumption of nonuniform magnetic field is more closer to the practical situation,which may yield the best result of spectral age.In this work,the average Chi-squared,²_red,values given by the KP model are higher than those by the JP and Tribble models,which likely results from its over simplified assumption on electron distribution and magnetic field.Therefore,JP and Tribble models are more suitable on spectral age investigations.The fourth chapter draws a conclusion on the whole investigations,and future prospects to research is addressed.