We explore the effective UV-optical albedos of a variety of types of broad emission line clouds, as well as their possible effects on the observed spectra of AGN. An important albedo source in moderately ionized ionization-bounded clouds is that due to neutral hydrogen: Rayleigh scattering of continuum photons off the extreme damping wings of Lya. The photons resulting from this scattering mechanism may contribute significantly to the Lya emission line, especially in the very broad wings. In addition, line photons emitted near 1200 Angstroms (e.g., N V 1240) that stream toward the neutral portion of the cloud may be reflected off this Rayleigh scattering mirror, so that they preferentially escape from the illuminated face. Inclusion of this effect can alter predicted emission line strengths and profiles. In more highly-ionized ionization-bounded clouds, Thompson scattering dominates the UV-optical albedo, but this albedo is lessened by the hydrogen gas opacity. These clouds are most reflective on the long wavelength side of the hydrogen recombination edges; this feature may then alter the shapes of the spectral regions near the recombination edges. We illustrate the effects of gas density and line broadening on the effective albedo. We also discuss the reflection effects of the accretion disk and the ``dusty torus.'' The accretion disk is an effective reflector of UV-optical photons, whether by electron or Rayleigh scattering, and it is possible that we observe a significant fraction of this light from the AGN in reflection. This effect can alter the emission line profiles and even destroy emission at the Lyman jump emitted by broad line clouds. Finally, we discuss the possibility that continuum reflection from broad line clouds is at least in part responsible for the polarized broad absorption line troughs.
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机译:我们探索了各种类型的宽发射线云的有效紫外光学反照率,以及它们对AGN观测光谱的可能影响。中度电离的离子云中一个重要的反照源是由于中性氢引起的:连续光子的瑞利散射离开了Lya的极端阻尼翼。由这种散射机制产生的光子可能对Lya发射谱线有很大贡献,特别是在非常宽的机翼中。另外,朝着云的中性部分流的接近1200埃(例如,N V 1240)发射的线光子可被该瑞利散射镜反射,使得它们优先从被照射的表面逸出。包含此效应可以改变预测的发射线强度和轮廓。在更多高度电离的离子束云中,汤普森散射占主导地位的紫外光学反照率,但是由于氢气的不透明性,这种反照率会降低。这些云在氢复合边缘的长波长一侧反射最强。该特征然后可以改变重组边缘附近的光谱区域的形状。我们说明了气体密度和谱线展宽对有效反照率的影响。我们还讨论了吸积盘和“尘土圆环”的反射效应。吸积盘是紫外线光学光子的有效反射器,无论是通过电子散射还是瑞利散射,我们都有可能观察到很大一部分该光从AGN反射出来。这种效应可以改变发射线轮廓,甚至破坏宽线云发射的莱曼跃迁处的发射。最后,我们讨论了从宽线云连续反射至少部分负责极化宽吸收线波谷的可能性。
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