论文标题

NGC1068的复杂红外尘埃连续发射:基于地面的N和Q波段以及新的辐射转移模型

The complex infrared dust continuum emission of NGC1068: ground-based N- and Q-band spectroscopy and new radiative transfer models

论文作者

Victoria-Ceballos, César Ivan, González-Martín, Omaira, Fritz, Jacopo, Almeida, Cristina Ramos, López-Rodríguez, Enrique, García-Burillo, Santiago, Alonso-Herrero, Almudena, Martínez-Paredes, Mariela, Esparza-Arredondo, Donaji, Osorio-Clavijo, Natalia

论文摘要

得益于地面红外和亚MM观察,对附近AGN的尘土飞扬的研究在过去几年中大大提高了。为了进一步研究原型Seyfert 2 Galaxy NGC1068的核中红外发射,在这里我们向N-和Q波段Michelle/Gemini Spectra提出了拟合。我们最初测试了几个可用的SED库,包括光滑,结块和两个相圆环模型,以及块状磁盘加风模型。虽然,如果我们允许在两个光谱频段之间改变某些模型参数,则光滑的圆环模型描述了NGC1068的光谱。在这个结果的促进下,我们使用辐射传输代码裙制作了新的SED。我们使用两个同心摩托车,使我们能够测试更复杂的几何形状。我们测试了内部和外部半径的不同值,幂律密度谱,不透明度和视角的一半开口角,径向和极性指数。此外,我们还测试了粉尘粒的大小以及硅酸盐晶粒的不同光学和量热特性。最佳拟合模型由两个同心成分组成,外部半径分别为1.8和28 PC。我们发现,灰尘结构中石墨和硅酸盐晶粒的大小以及光学和量热特性是重现NGC1068光谱的关键。我们得出的结论是,NGC1068中的灰尘达到了不同的尺度,其中中央和紧凑的成分给出了对中红外的最高贡献。存在一个较少密度和扩展的分量,这可以是同一圆环的一部分(构成喇叭盘),也可以代表极性灰尘成分的发射,如干涉测量值所建议的那样。

Thanks to ground-based infrared and sub-mm observations the study of the dusty torus of nearby AGN has greatly advanced in the last years. With the aim of further investigating the nuclear mid-infrared emission of the archetypal Seyfert 2 galaxy NGC1068, here we present a fitting to the N- and Q-band Michelle/Gemini spectra. We initially test several available SED libraries, including a smooth, clumpy and two phase torus models, and a clumpy disk plus wind model. Although, the smooth torus model describe the spectra of NGC1068 if we allow to vary some model parameters among the two spectral bands. Motivated by this result, we produced new SEDs using the radiative transfer code SKIRT. We use two concentric tori that allow us to test a more complex geometry. We test different values for the inner and outer radii, half opening angle, radial and polar exponent of the power-law density profile, opacity, and viewing angle. Furthermore, we also test the dust grains size and different optical and calorimetric properties of silicate grains. The best fitting model consists of two concentric components with outer radii of 1.8 and 28 pc, respectively. We find that the size and the optical and calorimetric properties of graphite and silicate grains in the dust structure are key to reproduce the spectra of NGC1068. We conclude that the dust in NGC1068 reaches different scales, where the highest contribution to the mid-infrared is given by a central and compact component. A less dense and extended component is present, which can be either part of the same torus (conforming a flared disk) or can represent the emission of a polar dust component, as already suggested from interferometric observations.

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