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arXiv 1809.09154astro-ph.GA
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ALMA揭示的Circinus星系中的环核多相气体

Circumnuclear Multi-phase Gas in the Circinus Galaxy II: The Molecular and Atomic Obscuring Structures Revealed with ALMA

Takuma Izumi, Keiichi Wada, Ryosuke Fukushige, Sota Hamamura, Kotaro Kohno

摘要:

我们使用阿塔卡马大型毫米/亚毫米阵列(ALMA)绘制了来自Circinus星系中心$\sim 200$ pc区域的CO(3 - 2)和[CI](1 - 0)线,以及它们的基础连续辐射,该区域拥有最近的2型塞弗特类活动星系核(AGN),空间分辨率为$\sim 6-15$ pc。线和连续发射区由一个环核盘(CND; 74 pc $\times$ 34 pc)和螺旋臂组成。连续辐射的分布揭示了一个依赖于温度的尘埃几何形状和可能的极地尘埃在环面区域的伸长率。CND的分子量为$M_{\rm H2} \sim 3 \times 10^6~M_\odot$,朝向活动星系核位置的束平均H $_2$柱密度为$\sim 5 \times 10^{23}$ cm $^{-2}$,这对核遮蔽有显著贡献。活动星系核位置的[CI](1 - 0)/CO(3 - 2)比值异常高,表明存在X射线主导的区域型化学。我们将观测到的速度场分解为旋转和色散分量,揭示了$r \lesssim 10$ pc环面区域的多相动力学性质,即,扩散的原子气体比致密的分子气体沿盘的垂直方向在空间上延伸得更多。通过与我们基于辐射驱动喷泉方案的模型预测的比较,我们表明原子流出是原子盘的几何厚度的驱动器。这支持了活动星系核附近的辐射驱动喷泉方案的有效性,这将解释长期存在的谜团,活动星系核环面的物理起源。

英文摘要:

We used the Atacama Large Millimeter/Submillimeter Array (ALMA) to map the CO(3-2) and [CI](1-0) lines, as well as their underlying continuum emission, from the central $\sim 200$ pc region of the Circinus galaxy that hosts the nearest type 2 Seyfert-class active galactic nucleus (AGN), with a spatial resolution of $\sim 6-15$ pc. The lines and continuum-emitting regions consist of a circumnuclear disk (CND; 74 pc $\times$ 34 pc) and spiral arms. The distribution of the continuum emission revealed a temperature-dependent dust geometry and possibly polar dust elongation in the torus region. The molecular mass of the CND is $M_{\rm H2} \sim 3 \times 10^6~M_\odot$ with a beam-averaged H$_2$ column density of $\sim 5 \times 10^{23}$ cm$^{-2}$ toward the AGN position, which contributes significantly to the nuclear obscuration. The [CI](1-0)/CO(3-2) ratio at the AGN position is unusually high, suggesting an X-ray dominated region-type chemistry. We decomposed the observed velocity fields into rotational and dispersion components, and revealed multi-phase dynamic nature in the $r \lesssim 10$ pc torus region, i.e., the diffuse atomic gas is more spatially extended along the vertical direction of the disk than the dense molecular gas. Through comparisons with our model predictions based on the radiation-driven fountain scheme, we indicate that atomic outflows are the driver of the geometrical thickness of the atomic disk. This supports the validity of the radiation-driven fountain scheme in the vicinity of this AGN, which would explain the long-lasting mystery, the physical origin of the AGN torus.

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