The Mid-Infrared Emission of Seyfert Galaxies: A New Analysis of ISOCAM Data

The Mid-Infrared Emission of Seyfert Galaxies: A New Analysis of ISOCAM Data
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Seyfert 星系的中红外发射：ISOCAM 数据的新分析

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发表时间：
2007
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通讯作者：
Jose Miguel Rodriguez Espinosa
Jose Miguel Rodriguez Espinosa
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作者：
C. R. Almeida;A. M. P. Garcia;J. Acosta;Jose Miguel Rodriguez Espinosa

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我们提供了用红外空间天文台(ISO)卫星上的ISOCAM仪器获得的57个活动星系核样本的中红外数据。图像通过LW2(6.75μm)和LW7(9.62μm)滤光片获得。这是对Clavel等人的一种新分析。星系样本，分为26个类型1(≤1.5)和28个类型2(&gt；1.5)塞弗特星系，外加3个类星体。图像的空间分辨率使我们能够在将亮度轮廓分解成不同的形态分量后，将核辐射和扩展辐射对总辐射的贡献分开。最常见的成分是中心点源(被标识为活动核)和指数盘。在某些情况下，需要一个凸起、一根棒或一个环。在Seyfert 1中，原子核对总发射的相对贡献比Seyfert 2大。这一结果证实了这两种类型的塞弗特星系在中红外波长范围内是不同的，并支持在该波长范围内存在产生各向异性发射的结构。我们还探索了中红外与射电和X射线波长范围之间的关系。在我们的样本中，对于星系的全球发射，保持了良好的无线电/红外关联。如果只考虑核红外发射，则光度-光度散点图中存在明显的非线性关联。对于类型2的塞弗特星系，本征硬X射线与核中红外发射之间的比率表现出大的散射和略大的值。这些结果似乎与围绕活跃核的块状尘埃环体的存在是一致的。
We present mid-infrared data of a sample of 57 AGNs obtained with the instrument ISOCAM on board the Infrared Space Observatory (ISO) satellite. The images were obtained through the LW2 (6.75 μm) and LW7 (9.62 μm) filters. This is a new analysis of the Clavel et al. galaxy sample, which is divided into 26 type 1 (≤1.5) and 28 type 2 (>1.5) Seyfert galaxies, plus three QSOs. The spatial resolution of the images allows us to separate the nuclear and the extended contributions to the total emission after decomposing the brightness profiles into different morphological components. The most common components are a central point source (identified as the active nucleus) and an exponential disk. In some cases a bulge, a bar, or a ring are needed. The relative contribution of the nucleus to the total emission appears larger in Seyfert 1 than in Seyfert 2 types. This result confirms that both types of Seyfert galaxies are different in the mid-infrared wavelength range and supports the existence of a structure which produces anisotropic emission in this wavelength range. We have also explored correlations between the mid-infrared and the radio and X-ray wavelength ranges. The well-established radio/infrared correlation is maintained in our sample for the global emission of the galaxies. If only the nuclear infrared emission is considered, then a nonlinear correlation is apparent in the luminosity-luminosity scatter diagram. The ratio between the intrinsic hard X-ray and the nuclear mid-infrared emission presents large scatter and slightly larger values for type 2 Seyfert galaxies. These results seem to be consistent with the presence of a clumpy dusty torus surrounding the active nucleus.