High-sensitivity VLBI observations of water masers in the Seyfert galaxy NGC 1068
High-sensitivity VLBI observations of water masers in the Seyfert galaxy NGC 1068
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塞弗特星系 NGC 1068 中水脉泽的高灵敏度 VLBI 观测
DOI：
10.1093/pasj/psac092
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发表时间：
2023
影响因子：
2.3
通讯作者：
Naomasa
中科院分区：
文献类型：
--
作者：
Morishima;Yuna ; Sudou;Hiroshi ; Yamauchi;Aya ; Taniguchi;Yoshiaki ; Nakai;Naomasa
我们展示了利用高灵敏度 22GHz 甚长基线干涉测量 (VLBI) 成像对赛弗特星系 NGC 1068 进行水蒸气脉泽发射的观测结果。在这个星系中，有以下四种核射电源； NE、C、S1 和 S2。其中，S1分量被确定为核，而C分量被认为归因于射电喷流。在我们的VLBI观测中，我们发现S1分量处有以下两种类型的水脉泽发射。一种是线性对齐的组件，被视为内半径为 0.62 pc 的边缘盘。通过假设圆周开普勒运动，估计内半径内的动力质量为 1.5 × 107M⊙。但请注意，最佳拟合旋转曲线显示亚开普勒旋转 (v∝r−0.24±0.10)。另一个是分布在旋转盘组件周围的水脉泽发射，距离 S1 组件高达 1.5 pc，表明 S1 组件存在双极流出。此外，我们首次利用VLBI检测到C分量中的水脉泽发射，并发现水脉泽发射呈环状分布。众所周知，分子云与 C 成分相关（ALMA 检测到 HCN 和 HCO+ 发射线）。因此，环形微波激射发射可以通过射流与分子云的碰撞来解释。然而，如果这些环状的水状云构成围绕C成分的旋转环，那么C成分很可能也有一个质量为∼106M⊙的超大质量黑洞，该黑洞可能由过去有核卫星星系的一次小合并提供。
We present observational results of water vapor maser emission with our high-sensitivity 22 GHz very long baseline interferometry (VLBI) imaging of the Seyfert galaxy NGC 1068. In this galaxy, there are the following four nuclear radio sources; NE, C, S1, and S2. Among them, the S1 component has been identified as the nucleus while the C component has been considered as attributed to the radio jet. In our VLBI observation, we find the following two types of water maser emission at the S1 component. One is a linearly aligned component that is considered as an edge-on disk with an inner radius of 0.62 pc. The dynamical mass enclosed within the inner radius was estimated to be 1.5 × 107M⊙by assuming the circular Keplerian motion. Note, however, that the best-fitting rotation curve shows a sub-Keplerian rotation (v∝r−0.24±0.10). The other is water maser emission distributed around the rotating disk component up to 1.5 pc from the S1 component, suggesting a bipolar outflow from the S1 component. Further, we detected water maser emission in the C component for the first time with VLBI, and discovered a ring-like distribution of water maser emission. It is known that a molecular cloud is associated with the C component (both HCN and HCO+emission lines are detected by ALMA). Therefore, the ring-like maser emission can be explained by the jet collision to the molecular cloud. However, if these ring-like water masing clouds constitute a rotating ring around the C component, it is likely that the C component also has a supermassive black hole with a mass of ∼106M⊙that could be supplied from a past minor merger of a nucleated satellite galaxy.