Circinus II的尘埃核心：利用MATISSE审视LM波段尘埃形态
The dusty heart of Circinus II. Scrutinizing the LM-band dust morphology using MATISSE
AI总结：
本文基于MATISSE首次对Circinus进行LM波段干涉观测，揭示了薄侧向圆盘与点源结构，确认其高遮蔽特性符合活动星系核统一模型，并通过改进辐射传输模型验证了辐射驱动喷泉模型。
摘要：
本文展示了Circinus的首次$L$波段和$M$波段干涉测量观测，该工作建立在近期$N$波段分析的基础之上。我们利用这些观测重建了图像，并对$L$和$M$波段拟合了高斯模型。我们的发现揭示了一个薄侧向圆盘，其宽度被勉强分辨，并且它是$N$波段成像的圆盘向更短波长的光谱延续。此外，我们在$L$和$M$波段发现了一个点源，基于$LMN$波段光谱能量分布拟合，该点源对应于$N$波段的点源。我们还证明，在Circinus的核周尘埃结构中，没有直接视线指向热尘埃表面的痕迹。假设尘埃存在，我们发现需要A$_{\rm V} \gtrsim 250$星等的遮蔽才能重现测得的通量。因此，所成像的圆盘可以在活动星系核统一模型中扮演遮蔽“环面”的角色。此外，我们探索了圆盘+双曲锥辐射传输模型的参数空间，并在锥底部确定了一处简单修改。在圆盘正上方和双曲锥底部内部添加一个团块簇，能更好地匹配中心孔径处观测到的温度分布。这与近期出现的辐射驱动喷泉模型非常吻合。只有VLTI独特的灵敏度和空间分辨率组合，才允许如此详细地审视和约束这类模型。我们计划在未来测试这种详细尘埃结构对其他MATISSE观测的活动星系核的适用性。
英文摘要：
In this paper we present the first-ever $L$- and $M$-band interferometric observations of Circinus, building upon a recent $N$-band analysis. We used these observations to reconstruct images and fit Gaussian models to the $L$ and $M$ bands. Our findings reveal a thin edge-on disk whose width is marginally resolved and is the spectral continuation of the disk imaged in the $N$ band to shorter wavelengths. Additionally, we find a point-like source in the $L$ and $M$ bands that, based on the $LMN$-band spectral energy distribution fit, corresponds to the $N$-band point source. We also demonstrate that there is no trace of direct sightlines to hot dust surfaces in the circumnuclear dust structure of Circinus. By assuming the dust is present, we find that obscuration of A$_{\rm V} \gtrsim 250$ mag is necessary to reproduce the measured fluxes. Hence, the imaged disk could play the role of the obscuring "torus" in the unified scheme of active galactic nuclei. Furthermore, we explored the parameter space of the disk + hyperbolic cone radiative transfer models and identify a simple modification at the base of the cone. Adding a cluster of clumps just above the disk and inside the base of the hyperbolic cone provides a much better match to the observed temperature distribution in the central aperture. This aligns well with the radiation-driven fountain models that have recently emerged. Only the unique combination of sensitivity and spatial resolution of the VLTI allows such models to be scrutinized and constrained in detail. We plan to test the applicability of this detailed dust structure to other MATISSE-observed active galactic nuclei in the future.
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