离轴辐照与活动星系核宽发射线的偏振
Off-axis irradiation and the polarization of broad emission lines in active galactic nuclei
摘要：
STOKES蒙特卡罗辐射转移程序已被扩展到模拟发射线偏振的速度依赖性。我们使用STOKES提出了改进的建模速度依赖的偏振活动星系核的宽发射线。我们证实，离轴连续发射可以产生所观察到的速度依赖性的程度和位置角的偏振。其特征是极化率的下降和极化位置角的S形摆动。我们的STOKES结果和以前的偏振模型之间的一些差异，由于离轴发射。特别是，我们发现，最大线通量和倾角的偏振百分比或摆动的位置角的中心速度之间的偏移的存在并不一定意味着散射材料是径向移动的。我们的模型是Smith等人（2005）描述的赤道散射盘的替代方案。我们讨论的战略，以区分这两种解释，并限制其相对贡献所观察到的速度分辨线和偏振。
英文摘要：
The STOKES Monte Carlo radiative transfer code has been extended to model the velocity dependence of the polarization of emission lines. We use STOKES to present improved modelling of the velocity-dependent polarization of broad emission lines in active galactic nuclei. We confirm that off-axis continuum emission can produce observed velocity dependencies of both the degree and position angle of polarization. The characteristic features are a dip in the percentage polarization and an S-shaped swing in the position angle of the polarization across the line profile. Some differences between our STOKES results and previous modelling of polarization due to off-axis emission are noted. In particular we find that the presence of an offset between the maximum in line flux and the dip in the percentage of polarization or the central velocity of the swing in position angle does not necessarily imply that the scattering material is moving radially. Our model is an alternative scenario to the equatorial scattering disk described by Smith et al. (2005). We discuss strategies to discriminate between both interpretations and to constrain their relative contributions to the observed velocity-resolved line and polarization.
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