Seyfert 2星系中隐宽线区与吸积率之间的联系
The Link Between the Hidden Broad Line Region and the Accretion Rate in Seyfert 2 Galaxies
摘要：
在过去的几年里，越来越多的证据被提出来，以修正被广泛接受的活动星系核统一模型。一个仅仅基于方向的模型不能解释所有观察到的现象。在下文中，我们将提出证据表明吸积率也是Seyfert 2星系中存在隐藏宽线区的关键参数。我们的样本由21个具有偏振隐藏宽线的源和18个不具有隐藏宽线的源组成。利用Seyfert 2星系中Ca Ⅱ和Mg b三重态的恒星速度色散，通过Mbh-σ \ast关系估计中心黑洞的质量.由内禀（即未被吸收的）X射线光度导出的辐射热光度与爱丁顿光度之间的比率，是物质吸积到中心超大质量黑洞上的速率的量度。康普顿薄HBLR和非HBLR源之间的分离是明确的，无论是在吸积率（log Lbol/LEdd = -1.9）和光度（log Lbol = 43.90）。当适当的亮度校正，康普顿厚源包括，HBLR和非HBLR之间的分离是不太尖锐，但没有HBLR源低于爱丁顿比阈值。我们推测，非HBLR康普顿厚源的吸积率高于阈值，确实拥有一个BLR，但一些东西，可能与他们的重吸收，是阻止我们观察它，即使在偏振光。我们的结果康普顿薄源支持理论预期。在Nicastro（2000）提出的一个模型中，宽发射线的存在与发生在过渡半径附近的盘不稳定性有内在联系，过渡半径是吸积率的函数，在吸积率很低的情况下，它变得比最里面的稳定轨道小，因此光度也很低。
英文摘要：
In the past few years more and more pieces of evidence have been presented for a revision of the widely accepted Unified Model of Active Galactic Nuclei. A model based solely on orientation cannot explain all the observed phenomenology. In the following, we will present evidence that accretion rate is also a key parameter for the presence of Hidden Broad Line Regions in Seyfert 2 galaxies. Our sample consists of 21 sources with polarized Hidden Broad Lines and 18 sources without Hidden Broad Lines. We use stellar velocity dispersions from several studies on the CaII and Mg b triplets in Seyfert 2 galaxies, to estimate the mass of the central black holes via the Mbh-σ\ast relation. The ratio between the bolometric luminosity, derived from the intrinsic (i.e. unabsorbed) X-ray luminosity, and the Eddington luminosity is a measure of the rate at which matter accretes onto the central supermassive black hole. A separation between Compton-thin HBLR and non-HBLR sources is clear, both in accretion rate (log Lbol/LEdd = -1.9) and in luminosity (log Lbol = 43.90). When, properly luminosity-corrected, Compton-thick sources are included, the separation between HBLR and non-HBLR is less sharp but no HBLR source falls below the Eddington ratio threshold. We speculate that non-HBLR Compton-thick sources with accretion rate higher than the threshold, do possess a BLR, but something, probably related to their heavy absorption, is preventing us from observing it even in polarized light. Our results for Compton-thin sources support theoretical expectations. In a model presented by Nicastro (2000), the presence of broad emission lines is intrinsically connected with disk instabilities occuring in proximity of a transition radius, which is a function of the accretion rate, becoming smaller than the innermost stable orbit for very low accretion rates and therefore luminosities.
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