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arXiv 1207.2668astro-ph.CO
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AGN中的光滑尘埃分布和杂乱尘埃分布:两种常用红外辐射模型的直接比较

Smooth and Clumpy Dust Distribution in AGN: a Direct Comparison of two Commonly Explored Infrared Emission Models

A. Feltre, E. Hatziminaoglou, J. Fritz, A. Franceschini

摘要:

活动星系核(AGN)内部尘埃的几何分布一直是一个有争议的问题,它直接关系到AGN的统一方案。传统上,在文献中讨论的模型假设两种不同的尘埃分布在被认为是超大质量黑洞周围的环形区域中:一种是连续分布,习惯上被称为平滑,另一种是尘埃集中在团块或云中,被称为团块。在本文中,我们进行了彻底的比较两个最流行的模型在文献中,即光滑模型弗里茨。等2006年和cluscular模型Nenkova等2008年a,在他们的共同参数空间。特别注意的是硅酸盐功能在~9.7和~18微米,红外线凸点的宽度,近红外线指数和光度在12.3微米,所有以前报道的可能的诊断工具,以区分两个尘埃分布。我们发现,由于在两个模型中使用的不同的粉尘化学成分,在9.7和18微米的硅酸盐特征的行为是相当不同的两个模型之间。红外凸起的宽度和红外发射的峰值可以取相当的值,但是它们的分布确实变化。近红外指数也有很大的不同,部分原因是两个模型采用的主要来源。具有匹配参数的模型不会产生类似的SED,并且几乎没有随机参数组合可以导致看似相同的SED。

英文摘要:

The geometry of the dust distribution within the inner regions of Active Galactic Nuclei (AGN) is still a debated issue and relates directly with the AGN unified scheme. Traditionally, models discussed in the literature assume one of two distinct dust distributions in what is believed to be a toroidal region around the Supermassive Black Holes: a continuous distribution, customarily referred to as smooth, and a concentration of dust in clumps or clouds, referred to as clumpy. In this paper we perform a thorough comparison between two of the most popular models in the literature, namely the smooth models by Fritz. et al. 2006 and the clumpy models by Nenkova et al. 2008a, in their common parameters space. Particular attention is paid to the silicate features at ~9.7 and ~18 micron, the width of the infrared bump, the near-infrared index and the luminosity at 12.3 micron, all previously reported as possible diagnostic tools to distinguish between the two dust distributions. We find that, due to the different dust chemical compositions used in the two models, the behaviour of the silicate features at 9.7 and 18 micron is quite distinct between the two models. The width of the infrared bump and the peak of the infrared emission can take comparable values, their distributions do, however, vary. The near-infrared index is also quite different, due partly to the primary sources adopted by the two models. Models with matched parameters do not produce similar SEDs and virtually no random parameter combinations can result in seemingly identical SEDs.

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