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arXiv 1010.5345astro-ph.CO
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类星体光谱中的取向效应:宽线区和窄线区

Orientation effects in quasar spectra: The broad- and narrow-line regions

Stephen Fine, Matt Jarvis, Tom Mauch

摘要:

我们使用SDSS,以及NVSS和WENSS定义了746个射电类星体的样本,并测量了它们的330 MHz至1.4GHz的光谱指数。按照以前的作者,我们采取的光谱指数作为一个指标的方向朝向类星体有更多的极上源具有平坦的光谱指数。我们使用这个代理的方向,调查的效果观察角度可能对光谱。光谱指数较平的类星体往往较亮。然而,我们没有发现任何迹象表明,在陡峭的光谱对象,以表明作为一个可能的解释模糊的环面。我们也没有发现增加的红化的平谱源,这可能意味着从喷流相关的排放的贡献。我们重现了先前描述的反相关性的MgII线的宽度和射电光谱指数表示一个磁盘状的几何形状的MgII BLR。与以前的作者相比,我们发现没有这样的相关性的CIV线建议一个更各向同性的高电离BLR。在陡谱源中,[OII]和[OIII]窄谱线都有较大的通量,而[OII]/[OIII]通量比较低。为了描述这两种效应,我们提出了一个简单的几何模型,其中NLR主要存在于面向活动核的光学厚云表面,并且NLR是分层的,使得更高的电离线优先靠近核。定量地,我们发现,方向可能会影响观察到的强度的窄线,以及线之间的比率,由一个因素~2。这些研究结果的影响,使用窄发射线估计热光度,以及窄线光度函数之间的比较类型1 s和类型2s,和潜在的发射线诊断图作为一个准确的工具,以区分AGN类。

英文摘要:

We use the SDSS, along with the NVSS and the WENSS to define a sample of 746 radio-loud quasars and measure their 330MHz to 1.4GHz spectral indexes. Following previous authors we take the spectral index as an indicator of the orientation towards the quasars with more pole-on sources having flatter spectral indexes. We use this proxy for orientation to investigate the effect observing angle may have on optical spectra. Quasars with flatter spectral indexes tend to be brighter. However, we find no indication of reddening in steep-spectrum objects to indicate obscuration by a torus as a possible explanation. Nor do we find increased redddening in the flat-spectrum sources which could imply a contribution from jet-related emission. We reproduce a previously-described anti-correlation between the width of the MgII line and radio spectral index indicating a disk-like geometry for the MgII BLR. In contrast to previous authors we find no such correlation for the CIV line suggesting a more isotropic high-ionisation BLR. Both the [OII] and [OIII] narrow lines have more flux in steep spectrum sources while the [OII]/[OIII] flux ratio is lower in these sources. To describe both of these effects we propose a simple geometric model in which the NLR exists primarily on the surface of optically thick clouds facing the active nucleus and the NLR is stratified such that higher-ionisation lines are found preferentially closer to the nucleus. Quantitatively we find that orientation may effect the observed strength of narrow lines, as well as ratios between lines, by a factor of ~2. These findings have implications for the use of narrow emission lines to estimate bolometric luminosities, as well as comparisons between narrow line luminosity functions for type 1s and type 2s, and the potential of emission-line diagnostic diagrams as an accurate tool with which to distinguish classes of AGN.

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