耀变体能量依赖同步辐射偏振的自洽建模及其在Mrk 421中的应用
Self-consistent modeling of energy-dependent synchrotron polarization in blazars with application to Mrk 421
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中文总结 AI 辅助
本研究通过自洽建模电子时变演化和俯仰角依赖的同步辐射，解释了耀变体X射线与光学偏振差异，并应用于Mrk 421，发现螺旋磁场可解释观测，无需能量分层喷流。
中文摘要 AI 辅助
对与我们的视线方向紧密对齐的黑洞喷流（即耀变体）的观测揭示，其X射线发射的偏振度可能显著高于光学波段。这种色偏振通常归因于能量分层喷流。在X射线发射由电子同步辐射主导的耀变体中，磁场线与电子速度之间的俯仰角也可能影响偏振度的频率依赖性，但这一效应在最先进的模型中通常被忽略。在本工作中，我们对耀变体的偏振和光谱能量分布进行建模，考虑了系统的时变演化以及依赖于俯仰角的电子同步辐射冷却。我们的分析研究了磁场结构和电子分布对偏振的影响，并检验这是否有助于解释观测到的偏振频率依赖性。通过扩展数值模拟代码AM3，我们加入了电子同步辐射发射的自洽计算，并模拟了多种磁场结构。我们将这些模型应用于Mrk 421，并与观测进行比较。最后，我们提出了一个时变激波喷流模型，以研究频率依赖的偏振角摆动。我们的结果展示了不同磁场结构如何影响能量依赖的偏振特征。对于Mrk 421，观测数据可以由喷流中的螺旋磁场解释。在激波喷流情景中，X射线偏振角变化了70度，而在光学/红外波段几乎保持不变。我们的结果表明，对电子时变演化的自洽处理对于模拟耀变体的偏振同步辐射发射至关重要，并且可以自然地解释色偏振特征，而无需假设能量分层喷流。
英文摘要
Observations of black hole jets closely aligned with our line of sight, known as blazars, have revealed that their X-ray emission can be significantly more polarized than in the optical bands. This chromatic polarization is often attributed to an energy-stratified jet. In blazars with X-ray emission dominated by electron synchrotron, the pitch angle between the magnetic field lines and electron velocity might also affect the frequency dependence of the polarization degree, but this effect is generally neglected in state-of-the-art models. In this work, we model the polarization and spectral energy distribution of blazars, accounting for the system's temporal evolution and pitch-angle-dependent electron synchrotron cooling. Our analysis investigates the impact of the magnetic field structure and electron distribution on polarization and tests whether this can help explain its observed frequency dependence. By extending the numerical simulation code AM3, we incorporate a self-consistent calculation of electron synchrotron emission and simulate various magnetic-field structures. We apply these models to Mrk 421 and compare them with observations. Finally, we present a time-dependent shock-in-jet model to investigate frequency-dependent polarization angle swings. Our results show how different magnetic-field structures affect energy-dependent polarization signatures. In the case of Mrk 421, the data can be explained by a helical field in the jet. In the shock-in-jet scenario, the X-ray polarization angle changes by 70 degrees, while remaining almost constant in the optical/infrared. Our results demonstrate that a self-consistent treatment of the temporal evolution of electrons is essential to model the polarized synchrotron emission from blazars and can naturally explain chromatic polarization signatures without requiring an energy-stratified jet.
发表机构
- Centre for Space Research, North-West University（北威特大学空间研究中心）
- Instituto de Física, Universidade Federal de Goiás（戈亚斯联邦大学物理研究所）
- Université Paris Cité, CNRS, Astroparticule et Cosmologie（巴黎西岱大学，法国国家科学研究中心，亚原子粒子与宇宙学）
- Ruhr Astroparticle and Plasma Physics Center (RAPP Center)（鲁尔天体粒子与等离子体物理中心（RAPP中心））
- Ruhr University Bochum, Faculty of Physics and Astronomy, Astronomical Institute (AIRUB)（波鸿鲁尔大学，物理与天文学院，天文研究所（AIRUB））
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