Blueshifted outflow from 24.329+0.145
Blueshifted outflow from 24.329+0.145
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流出量从 24.329 蓝移 0.145
DOI：
10.1111/j.1365-2966.2010.17856.x
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发表时间：
2011
影响因子：
4.8
通讯作者：
J. Green
中科院分区：
文献类型：
--
作者：
J. Caswell;J. Green
对羟基 (OH) 脉泽位点的新研究表明，它的发射产生于独特的强蓝移外流中，该位点困扰了天文学家 40 多年。使用澳大利亚望远镜紧凑阵列 (ATCA) 进行的测量将这个神秘的 OH 1667 MHz 脉泽定位在 24.329+0.145（银河坐标）处。这与甲醇 6668 MHz 跃迁处的脉泽发射和水的 22 GHz 跃迁处新发现的脉泽发射一致（达到弧秒精度）。甲醇微波激射器将该地点确定为大质量恒星形成的地点之一，而甲醇的小扩散特征大约为 +113 km s−1 的中值速度，定义了其系统速度。水脉泽显示出在该系统速度附近产生的一些发射和在蓝移流出中产生的其余部分的组合。
1667 MHz OH 发射范围超过 20 km s−1，我们与甲醇微波激射器的关联表明，它与系统速度的偏移量高达 50 km s−1。隐含的能量蓝移流出在此类 OH 脉泽中是前所未有的。我们使用 ATCA 和新型高分辨率光谱仪进行的光谱研究，实现了 1665 MHz 和 1667 MHz OH 基态跃迁的全偏振观测。 1667 MHz 发射占主导地位，而在 1665 MHz 处没有检测到，表明流出区域具有不寻常的物理特性。同样，线性偏振的普遍存在可能是快速移动的流出中产生发射的结果，线性偏振方向和流出方向之间可能存在联系。
我们还提出了脉塞位点 24.494−0.039 和 24.790+0.083 的新观测结果。这些 24.329+0.145 的近邻，以相似的系统速度发射甲醇脉泽，也伴随着水和 OH 的脉泽，但没有不寻常的脉泽特性。所有三个地点以及 H ii 复合体 W42 的速度和银河经度对应于 3-kpc 臂（膨胀环）切点附近的一个特别有趣的银河位置，距离 7.7 kpc。
New studies of an hydroxyl (OH) maser site that has puzzled astronomers for more than 40 yr demonstrate that its emission arises in a unique strong blueshifted outflow. Measurements with the Australia Telescope Compact Array (ATCA) locate this enigmatic OH 1667-MHz maser at 24.329+0.145 (Galactic coordinates). This is coincident (to arcsecond accuracy) with maser emission at the 6668-MHz transition of methanol and a newly discovered maser at the 22-GHz transition of water. The methanol maser establishes the site as one of high-mass star formation, and the small spread of methanol features about a median velocity of +113 km s−1 defines its systemic velocity. The water maser shows a combination of some emission arising near this systemic velocity, and the remainder arising in the blueshifted outflow.
The 1667-MHz OH emission extends over more than 20 km s−1, and our demonstrated association with the methanol maser reveals that this is offset from the systemic velocity by as much as 50 km s−1. The implied energetic blueshifted outflow is unprecedented in OH masers of this class. Our spectral studies using the ATCA, with a new high-resolution spectrometer, achieve full polarization observations of the 1665- and 1667-MHz OH ground-state transitions. The dominance of 1667-MHz emission, with no detection at 1665 MHz, suggests unusual physical properties in the ouflow region. Likewise, the prevalence of linear polarization may be a consequence of emission arising in a fast-moving outflow, with perhaps a link between linear polarization orientation and outflow orientation.
We also present new observations of maser sites 24.494−0.039 and 24.790+0.083. These close neighbours of 24.329+0.145, with methanol maser emission at a similar systemic velocity, are also accompanied by masers of water and OH, but have no unusual maser properties. The velocity and Galactic longitude of all three sites, and of the H ii complex W42, correspond to an especially interesting Galactic location near the tangent point of the 3-kpc arm (expanding ring), at a distance of 7.7 kpc.