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arXiv 1204.0940astro-ph.HE
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从光学到X射线波段无线电静默AGN的偏振建模

Modeling the polarization of radio-quiet AGN from the optical to the X-ray band

Frederic Marin, Rene W. Goosmann

摘要:

热活动星系核(AGN)由一个强有力的宽带连续辐射源组成,辐射源周围环绕着几种不同几何形状和成分的后处理介质。在这里,我们调查预期的光谱偏振签名在光学/UV和X射线波段,因为它们产生的复杂的辐射耦合之间的不同,轴对称活动星系核介质。使用最新版本的蒙特卡罗辐射转移代码STOKES,我们得到的光谱通量,偏振百分比,和偏振位置角。在光学/UV中,我们假设非偏振光子来自一个紧凑的源,该源被光学厚的尘埃环面以及赤道和极性电子散射区域重新处理。在X射线波段,我们还假设一个灯柱几何结构,一个X射线源从上面照射吸积盘。我们比较我们的结果为两个波段,从而为未来的X射线偏振任务提供预测。这些预测可以基于目前的光学/紫外分光偏振观测。特别是,我们得出结论,在光学/UV波段观察到的偏振二分法应延伸到X射线范围。

英文摘要:

A thermal active galactic nucleus (AGN) consist of a powerful, broad-band continuum source that is surrounded by several reprocessing media with different geometries and compositions. Here we investigate the expected spectropolarimetric signatures in the optical/UV and X-ray wavebands as they arise from the complex radiative coupling between different, axis-symmetric AGN media. Using the latest version of the Monte-Carlo radiative transfer code STOKES, we obtain spectral fluxes, polarization percentages, and polarization position angles. In the optical/UV, we assume unpolarized photons coming from a compact source that are reprocessed by an optically-thick, dusty torus and by equatorial and polar electron-scattering regions. In the X-ray band, we additionally assume a lamp-post geometry with an X-ray source irradiating the accretion disk from above. We compare our results for the two wavebands and thereby provide predictions for future X-ray polarimetric missions. These predictions can be based on present-day optical/UV spectropolarimetric observations. In particular, we conclude that the observed polarization dichotomy in the optical/UV band should extend into the X-ray range.

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