典型活动星系核中喷流的辐射机制研究
文献类型：学位论文
| 作者 | 刘文泼 |
| 学位类别 | 博士 |
| 答辩日期 | 2009-05-12 |
| 授予单位 | 中国科学院上海天文台 |
| 授予地点 | 上海天文台 |
| 导师 | 沈志强 |
| 关键词 | 活动星系核 喷流 辐射机制 非热辐射 |
| 其他题名 | Research on Emission Mechanisms of Jets in Typical AGNs |
| 中文摘要 | In this dissertation, we mainly discuss the radiation mechanisms for the jets in typical AGNs (such as jets in M87, 3C 273 etc.).Research on the two typical jets could not only improve our understanding of the jets with large (M87 jet) and small (3C 273 jet) viewing angles, but also help to systemically explore the nature of jets. For M87 jet (large viewing angle jet), we proposed a modified synchrotron model which could explain the broad band spectral shape of knots in it. This model considers the integrated effect of particle injection from different acceleration sources in the thin acceleration region. So there are two break frequencies at two sides of which the spectral index of the M87 knots changes. The observed flux of the M87 knots from radio to X-ray can be well fitted by the model, and the predicted spectra from ultraviolet to X-ray could be further tested by future observations. The model points out that the knots D, E, F, A, B, and C1 are unlikely to be the candidate for the TeV emission recently detected in M87. For 3C 273 jet (small viewing angle jet), we present a promoted stratified jet model to interpret the observed spectral energy distributions of knots in it. Based on the hypothesis of the single index of the particle energy spectrum at injection and identical emission processes among all the knots, the observed difference of spectral shape among different 3C 273 knots can be understood as a manifestation of deviation of the equivalent Doppler factor of stratified emission regions in individual knot from a characteristic one. The summed spectral energy distribution of all the ten knots in 3C 273 jet can be well fitted by two components, low-energy (radio to optical) component dominated by the synchrotron radiation and high-energy componen (UV, X-ray and $\gamma$-ray) dominated by the inverse Compton scattering of the cosmic microwave background. This gives a consistent spectral index of $\alpha = 0.88$ ($S_\nu \propto \nu^{-\alpha}$) and a characteristic Doppler factor of 7.4. Assuming the average of the summed spectrum as the characteristic spectrum of each knot in the 3C 273 jet, we further get a distribution of Doppler factor. We discuss the possible implications of these results for the physical properties in the 3C 273 jet. Future GeV observations could separate the $\gamma$-ray emission of 3C 273 from the large scale jet and the small scale jet (i.e. the core) through measuring the GeV spectrum. Furthermore, we applied the stratified jet model for 3C 273 jet to the FSRQs' jets (such as (small viewing angle) jets in PKS 1136-135 and PKS 1150+497) and have obtained some interesting results which could be verified by observations---these imply that the stratified jet model may help to systemically explore the nature of jets in AGNs. In the future, we will continue to systemically explore the nature of jets using the promoted stratified jet model (Liu \& Shen 2007, 2009) to interpret the radiation and acceleration mechanism of the jets in AGNs. Furthermore, we also try to apply the synchrotron model to other sources (such as knot HST-1 in the M87 jet etc.). |
| 英文摘要 | 本文主要讨论了M87和3C 273等活动星系核中喷流的辐射机制。M87喷流是典型的大视角喷流，而3C 273喷流是典型的小视角喷流，研究这两个典型喷流，不仅可以增进我们对不同视角喷流的认识，而且也有助于我们系统地探索喷流的本质。 关于M87喷流我们提出了一种修正的同步辐射模型，该模型可以解释M87喷流中亮结的宽波段(射电到X-ray波段)辐射谱型。模型考虑了加速区内不同源粒子传输到辐射区时所产生的集体效应，这导致 M87亮结的能谱分布出现两个折断频率(break frequency)，而辐射谱指数在折断频率两边也发生了改变。这很自然地解释了M87亮结的能谱分布，同时给出了紫外到X射线的谱型预言。最后模型还指出，亮结D, E, F, A, B和C1不可能是M87的TeV辐射候选体。 关于3C 273喷流，我们提出了一种推广的分层喷流模型，认为喷流中粒子簇近似按能量分层分布，即高能粒子簇集中在喷流主轴附近而低能粒子簇主要分布在喷流外层，分层粒子簇的内禀速度和视角 可能是不同的，在小视角情况下，这会导致分层粒子簇多普勒因子的敏感变化，该模型可以解释3C 273喷流的观测能谱分布。 我们把针对3C 273这类小视角喷流而提出的推广的分层模型应用到了PKS 1136-135和PKS 1150+497等喷流中，也得到了一些有趣的结论(其中一个研究亮点就是，我们预言PKS 1150+497喷流对GeV辐射的贡献也许可以通过FERMI一年全天空巡天观测进行检验)---这些暗示了分层模型对于系统地认识喷流本质是有效的。 而应用分层模型系统地认识喷流也是下一步我们进行关于喷流辐射机制的大样本统计性研究的一个动机。此外，我们也试图将同步辐射辐射模型进一步应用到其它源上(例如M87中亮结HST-1等)。 |
| 语种 | 中文 |
| 公开日期 | 2011-07-01 |
| 页码 | 95 |
| 源URL | [http://119.78.226.72//handle/331011/14748]  |
| 专题 | 上海天文台_中国科学院上海天文台学位论文 |
| 推荐引用方式 GB/T 7714 | 刘文泼. 典型活动星系核中喷流的辐射机制研究[D]. 上海天文台. 中国科学院上海天文台. 2009. |
入库方式： OAI收割
来源：上海天文台
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