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arXiv 1710.03419astro-ph.GA
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作为活动星系核中宽发射线起源的潮汐破裂尘埃团

Tidally disrupted dusty clumps as the origin of broad emission lines in active galactic nuclei

Jian-Min Wang, Pu Du, Michael S. Brotherton, Chen Hu, Yu-Yang Songsheng, Yan-Rong Li, Yong Shi, Zhi-Xiang Zhang

摘要:

1型活动星系核显示出宽的发射谱线,被认为是由在超大质量黑洞引力势中运动的光电离气体引起的。然而,到目前为止,这种宽线区域气体的起源还没有得到解决。另一个组成部分是宽线区域之外的尘埃环面,可能是离散团块的集合,可以从某些视角隐藏该区域,并使它们在观测上看起来像2型物体。在这里,我们报告说,这些团块在尘埃升华半径内移动,就像在银河系中心发现的分子云G2一样,将被黑洞潮汐破坏,导致一些气体被束缚在较小的半径,而其他气体则被喷射并返回到环面。团簇满足被光电离的必要条件。潮汐扰动团块的特定动力学成分包括作为流入的螺旋气体、作为流出的循环气体和作为流出的喷出物。我们计算了这些云的各种发射线轮廓,发现它们与Palomar-Green类星体的H $β$轮廓基本一致。我们发现,不对称,形状和转移的配置文件强烈依赖于[O III],光度,我们解释为代理的尘埃环面角。来自环面的潮汐破裂团块可能代表宽线区气体的来源。

英文摘要:

Type 1 active galactic nuclei display broad emission lines, regarded as arising from photoionized gas moving in the gravitational potential of a supermassive black hole. The origin of this broad-line region gas is unresolved so far, however. Another component is the dusty torus beyond the broad-line region, likely an assembly of discrete clumps that can hide the region from some viewing angles and make them observationally appear as Type 2 objects. Here we report that these clumps moving within the dust sublimation radius, like the molecular cloud G2 discovered in the Galactic center, will be tidally disrupted by the hole, resulting in some gas becoming bound at smaller radii while other gas is ejected and returns to the torus. The clumps fulfill necessary conditions to be photoionized. Specific dynamical components of tidally disrupted clumps include spiral-in gas as inflow, circularized gas, and ejecta as outflow. We calculate various profiles of emission lines from these clouds, and find they generally agree with H$β$ profiles of Palomar-Green quasars. We find that asymmetry, shape and shift of the profiles strongly depend on [O III], luminosity, which we interpret as a proxy of dusty torus angles. Tidally disrupted clumps from the torus may represent the source of the broad-line region gas.

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