中红移类星体III中H β区的VLT/ISAAC光谱。β宽谱分析及对BLR结构的推断
VLT/ISAAC Spectra of the Hbeta Region in Intermediate-Redshift Quasars III. Hbeta Broad Line Profile Analysis and Inferences about BLR Structure
摘要：
[摘要]我们提供了30个类星体的新VLT ISAAC光谱，我们将其与以前的数据相结合，产生了53个中间红移（z ~ 0.9 - 3.0）源的样本。该样本用于探索这些非常明亮的类星体的Hbeta光谱区域中的突出线条的特性。我们发现了两个主要趋势：（1）最小半高宽H β随光度的系统性增加（在以前的论文中讨论过）。这个较低的半高宽包络是最好的拟合，假设最西源辐射接近爱丁顿极限，显示线发射从维里化云分布，并遵守一个定义良好的宽线区域大小与光度的关系。(2)[OIII]的等效宽度（从W ~ 15到~ 1A）随源测热光度的增加（从log L ~ 43到log L ~ 49）而系统地减小。进一步确定的趋势需要区分所谓的A类和B类来源。我们产生的中值复合光谱在六个光度箱流行。A源显示合理的对称洛伦兹Hbeta配置文件在所有的光度，而流行。B源需要两个组件适合涉及一个未移动的广泛和红移非常广泛的组件。非常宽的H β强度随着L的增加而增加，而宽分量保持不变，导致明显的“鲍德温效应”，在我们的样品光度范围内，等效宽度从W ~ 80 A减小到~ 20 A。大致恒定的等效宽度所示的Hbeta非常广泛的组成部分意味着在光学厚，光电离气体的生产。红移的非常宽的分量的开始似乎是一个临界变化，发生在Pop. A-B边界附近，半高宽Hbeta ~ 4000 km/s，我们将其与临界爱丁顿比（~ 0.2 +/- 0.1）联系起来。
英文摘要：
[Abridged] We present new VLT ISAAC spectra for 30 quasars, which we combine with previous data to yield a sample of 53 intermediate redshift (z ~ 0.9 - 3.0) sources. The sample is used to explore properties of prominent lines in the Hbeta spectral region of these very luminous quasars. We find two major trends: (1) a systematic increase of minimum FWHM Hbeta with luminosity (discussed in a previous paper). This lower FWHM envelope is best fit assuming that the narrowest sources radiate near the Eddington limit, show line emission from a virialized cloud distribution, and obey a well defined broad line region size vs. luminosity relation. (2) A systematic decrease of equivalent width of [OIII] (from W ~ 15 to ~ 1 A) with increasing source bolometric luminosity (from log L ~ 43 to log L ~ 49). Further identified trends required discrimination between so-called Population A and B sources. We generate median composite spectra in six luminosity bins Pop. A sources show reasonably symmetric Lorentzian Hbeta profiles at all luminosities while Pop. B sources require two component fits involving an unshifted broad and a redshifted very broad component. Very broad Hbeta increases in strength with increasing L while the broad component remains constant resulting in an apparent "Baldwin effect" with equivalent width decreasing from W ~ 80 to ~ 20 A over our sample luminosity range. The roughly constant equivalent width shown by the Hbeta very broad component implies production in optically-thick, photoionized gas. The onset of the redshifted very broad component appears to be a critical change that occurs near the Pop. A-B boundary at FWHM Hbeta ~ 4000 km/s which we relate to a critical Eddington ratio (~ 0.2 +/- 0.1).
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