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arXiv 1104.1348astro-ph.CO
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[ OIII ] 5007 A等效宽度与AGN遮蔽度的关系

The relationship between [OIII]5007A equivalent width and obscuration in AGN

A. Caccianiga, P. Severgnini

摘要:

本文研究了活动星系核中[OIII] 5007 A窄发射线的等效宽度(EW)与活动星系核的遮蔽水平之间的关系。为此,我们结合了一个系统的光谱分析的结果,无论是在光学和X-射线,在统计上完整的样本~170 X-射线选择AGN从XMM-牛顿明亮的偶发源样本(XBS)。我们发现,在样品中观察到的大范围的[OIII] 5007 A等效宽度(从几个A到500 A)可以很好地解释为固有的扩展的组合,可能是由于窄线区域的覆盖因子的大范围,以及吸收的影响。在40- 50 A以下的EW中,本征展宽占主导地位,而吸收使EW值达到~100- 150 A,对于中等水平的吸收(AV~0.5-2 mag)或AV>2 mag的EW值达到~ 500 A。使用数值模拟,我们发现,这个模型是能够再现的[OIII] 5007 A EW分布中观察到的XBS样本,并正确地预测的形状观察到的EW分布的光学选择的样本中的类星体从SDSS调查。

英文摘要:

In this paper we study the relationship between the equivalent width (EW) of the [OIII]5007A narrow emission line in AGN and the level of obscuration. To this end, we combine the results of a systematic spectral analysis, both in the optical and in the X-rays, on a statistically complete sample of ~170 X-ray selected AGN from the XMM-Newton Bright Serendipitous Source sample (XBS). We find that the observed large range of [OIII]5007A equivalent widths observed in the sample (from a few A up to 500A) is well explained as a combination of an intrinsic spread, probably due to the large range of covering factors of the Narrow Line Region, and the effect of absorption. The intrinsic spread is dominant for EW below 40-50A while absorption brings the values of EW up to ~100-150A, for moderate levels of absorption (AV~0.5-2 mag) or up to ~500A for AV>2 mag. In this picture, the absorption has a significant impact on the observed EW also in type~1 AGN. Using numerical simulations we find that this model is able to reproduce the [OIII]5007A EW distribution observed in the XBS sample and correctly predicts the shape of the EW distribution observed in the optically selected sample of QSO taken from the SDSS survey.

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