耀变体的喷流物理研究

The Study on the Physical Properties of Blazar Jets

活动星系核（AGN）是一类特殊的活动星系,核心存在着猛烈的活动现象和剧烈的物理过程.耀变体（blazar）是活动星系核的一个子类,其具有相对论性喷流且喷流视角很小,因此集束效应较强,观测到的辐射基本都来自于喷流.相对论性喷流物理还很不清楚,如喷流的形成、喷流的准直和喷流的物质成分等.耀变体多波段辐射为喷流主导,为研究喷流物理提供了理想的实验室.本论文第1章介绍了AGN和blazar研究的部分进展.第2章进一步介绍了blazar常用的喷流模型.

Active galactic nuclei （AGNs） belong to a special class of active galaxies, and have violent active phenomena and intense physical processes in the nuclei. Blazar is a subclass of AGNs, and has a relativistic jet with a small jet viewing angle. Therefore, the boosting effect is very important, and almost all the observed radiation is dominated by the jet. The relativistic jet physics is not very clear yet, such as the jet formation, collimation, and matter content etc. The multi-waveband radiation of blazar is dominated by jet, which provides an ideal laboratory for studying the jet physics. The first chapter of this thesis introduces the recent progress of AGNs and blazars. We further introduce the jet model that commonly used in blazars in the second chapter. In the third chapter, we fit simultaneously （or quasi-simultaneously） the multi-waveband spectral energy distributions （SEDs） for a sample of low-synchrotron-peaked （LSP） blazars with the jet model and X2 procedure, which takes into account different soft photon fields （broad line region or a molecular torus）. We find that the SED fitting with an external soft photon from IR torus is systematically better than that from the broad line region （BLR） based on a X2 test, which suggests that the 7-ray emitting region most possibly stays outside the BLR. The minimum electron Lorentz factor, ＂fmin, is constrained from the modeling of these LSP blazars with good soft X-ray data, and in a range from 5 to 160 （with a median value of 55）, which plays a key role in jet power estimation. Assuming one-to-one ratio of proton and electron, we find that the jet power for LSP blazars is systematically higher than that of Fanaroff-Riley type II （FR II） radio galaxies. A possible reason for this is that there are some positrons in the jets of these blazars. If this is the case, the jet power will be reduced. Therefore, we propose a mixed composition of ei - p in the jets of these LSP blazars. If we assume that the jet power of LSP blazars is the same as that of FR Hs, we find that it is an electron-positron pair dominated leptonic jet in these blazars, and the number density of electron-positron pairs is several times higher than that of electron-proton pairs, but the jet power is still dominated by protons.