Nonthermal radiation from jets of active galactic nuclei: Electrostatic bremsstrahlung as alternative to synchrotron radiation
Nonthermal radiation from jets of active galactic nuclei: Electrostatic bremsstrahlung as alternative to synchrotron radiation
复制标题
活跃星系核喷流的非热辐射：静电轫致辐射替代同步加速器辐射
DOI：
10.1051/0004-6361:20031103
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发表时间：
2003
影响因子：
6.5
通讯作者：
R. Schlickeiser
中科院分区：
文献类型：
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作者：
R. Schlickeiser
活动星系核的平行相对论性强子和轻子喷流与周围的星际和星系间介质相互作用，由于双流不稳定性，在同向运动的喷流区产生了能量密度大于磁场能量密度的巨大的亚光速静电（朗缪尔）波场。因此，我们重新审视静电韧致辐射，即高能正电子和电子对光子的静电波的逆康普顿散射（l + e → t + e ′），作为同步辐射的替代非热辐射过程，在文献中，同步辐射是辐射的标准低频辐射过程。已知这种辐射过程具有与同步加速器辐射类似的偏振特性。通过计算多普勒增强的光度谱的情况下，轻子外流，我们表明，在射流流出源的静电韧致辐射扫起来的相对论电子是强于同步辐射从相同的电子在无线电光学频带，而光学厚体静电韧致辐射从非相对论对流出等离子体通常是一个因素10 - 10小。我们的分析是基于光子角积分单色近似的静电轫致辐射功率和同步辐射功率在等离子体中，这是从单电子和正电子的各自的辐射功率的时刻构造。针对Schlickeiser等人（2002）的轻子喷流模型中特定的亚光速静电波分布和上扫相对论电子，我们计算了标准内喷流参数下体定常韧致辐射、相对论电子韧致辐射和同步辐射的预期多普勒增强辐射强度。这需要详细研究（i）辐射电子的平衡分布和（ii）每个辐射过程的发射和吸收系数。静电韧致辐射机制的一个吸引人的特点是喷流与周围环境介质的相互作用产生了目标静电等离子体波和辐射扫掠的相对论电子。它不依赖于大的内禀有序磁场的存在来解释由于同步辐射过程而产生的强发射。这对于远离中心喷气发动机的非热辐射也可能是重要的。
The interaction of collimated relativistic hadronic and leptonic jet outflows from active galactic nuclei with the sur- rounding interstellar and intergalactic medium generates by two-stream instabilities huge intensities of subluminal electrostatic (Langmuir) wave fields in the co-moving outflow region with energy densities larger than the energy density in the magnetic field. We therefore revisit electrostatic bremsstrahlung, i.e. the inverse Compton scattering of electrostatic waves by energetic positrons and electrons to photons (l + e → t + e � ), as an alternative nonthermal radiation process to synchrotron radiation which in the literature sofar has been the standard low-frequency radiation process for radiation. It is known that this radiation process has similar polarisation properties as synchrotron radiation. By calculating Doppler boosted luminosity spectra in case of leptonic outflows we demonstrate that in jet outflow sources electrostatic bremsstrahlung by swept-up relativistic electrons is stronger than synchrotron radiation from the same electrons in the radio to optical frequency band, whereas the optically thick bulk electrostatic bremsstrahlung from the non-relativistic pair outflow plasma is typically a factor 10 10 smaller. Our analysis is based on photon angle integrated monochromatic approximations of the electrostatic bremsstrahlung power and synchrotron radiation power in a plasma, which are constructed from moments of the respective radiation powers of single electrons and positrons. Specialising to the specific subluminal electrostatic wave distribution and the swept-up relaivistic electrons in the leptonic jet model of Schlickeiser et al. (2002) we calculate the expected Doppler boosted radiation intensities from bulk elec- trostatic bremsstrahlung, relativistic electron bremsstrahlung and synchrotron radiation for standard inner jet parameters. This requires to investigate in detail (i) the equilibrium distribution of the radiating electrons and (ii) the emission and absorption coefficients of each radiation process. An attractive feature of electrostatic bremsstrahlung mechanism is the fact that the in- teraction of the jet outflow with the surrounding ambient medium generates both the target electrostatic plasma waves and the radiating swept-up relativistic electrons. It does not rely on the existence of large intrinsic ordered magnetic fields to account for strong emission due to the synchrotron radiation process. This might be of importance also for nonthermal emission far away from the central jet engine.