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arXiv 1206.0777astro-ph.CO
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低光度活动星系核的高空间分辨率SED

The SED of Low-Luminosity AGNs at high-spatial resolution

J. A. Fernández-Ontiveros, M. A. Prieto, J. A. Acosta-Pulido, M. Montes

摘要:

活动星系核的内部结构在一定的光度极限以下会发生变化。大的蓝色凸起是吸积盘的足迹,在大多数低光度活动星系核中是不存在的。此外,最近的模拟表明,统一模型中的一个关键环,对于L_bol < 10^42 erg/s的原子核消失了。然而,由于宿主星系的贡献,LLAGN的研究是一项复杂的任务,它的光淹没了这些暗淡的核。这是特别关键的红外范围内,在最大的环面发射,由于旧的恒星星族和/或尘埃的贡献,在核区域。自适应光学成像在近红外(VLT/NaCo)与衍射限制成像在中红外(VLT/VISIR)允许我们隔离的一些最近的LLAGN在南半球的核发射。这些数据被扩展到光学/紫外范围(HST),无线电(VLA,VLBI)和X射线(Chandra,XMM-Newton,Integral),以便在整个光谱范围内建立具有一致空间分辨率(< 0.5”)的每个AGN的真正光谱能量分布(SED)。从各个SED,我们构建了一个平均SED的LLAGN采样在所有波段之前提到的。与以前的多波长研究的LLAGNs相比,这项工作涵盖了高空间分辨率数据的中红外和近红外范围。样品中的LLAGN在SED形状方面呈现出很大的多样性。它们中的一些可以用自吸收同步加速器(例如NGC 1052)很好地描述,而另一些则呈现出约1微米的类热凸点(NGC 4594)。与明亮的Seyferts和类星体相比,它们都有显著的不同,这表明活动星系核的内部结构(即环面和吸积盘)在低光度下发生了内在的变化。

英文摘要:

The inner structure of AGNs is expected to change below a certain luminosity limit. The big blue bump, footprint of the accretion disk, is absent for the majority of low-luminosity AGNs (LLAGNs). Moreover, recent simulations suggest that the torus, a keystone in the Unified Model, vanishes for nuclei with L_bol < 10^42 erg/s. However, the study of LLAGN is a complex task due to the contribution of the host galaxy, which light swamps these faint nuclei. This is specially critical in the IR range, at the maximum of the torus emission, due to the contribution of the old stellar population and/or dust in the nuclear region. Adaptive optics imaging in the NIR (VLT/NaCo) together with diffraction limited imaging in the mid-IR (VLT/VISIR) permit us to isolate the nuclear emission for some of the nearest LLAGNs in the Southern Hemisphere. These data were extended to the optical/UV range (HST), radio (VLA, VLBI) and X-rays (Chandra, XMM-Newton, Integral), in order to build a genuine spectral energy distribution (SED) for each AGN with a consistent spatial resolution (< 0.5") across the whole spectral range. From the individual SEDs, we construct an average SED for LLAGNs sampled in all the wavebands mentioned before. Compared with previous multiwavelength studies of LLAGNs, this work covers the mid-IR and NIR ranges with high-spatial resolution data. The LLAGNs in the sample present a large diversity in terms of SED shapes. Some of them are very well described by a self-absorbed synchrotron (e.g. NGC 1052), while some other present a thermal-like bump at ~1 micron (NGC 4594). All of them are significantly different when compared with bright Seyferts and quasars, suggesting that the inner structure of AGNs (i.e. the torus and the accretion disk) suffers intrinsic changes at low luminosities.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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