REVISING THE KINEMATICS OF 12 GHz CH3OH MASERS TOWARD W3(OH)
REVISING THE KINEMATICS OF 12 GHz CH3OH MASERS TOWARD W3(OH)
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DOI：
10.1088/0004-637x/716/2/1356
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发表时间：
2010-04
期刊：
影响因子：
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通讯作者：
L. Moscadelli;Ye Xu;Xi Chen
中科院分区：
文献类型：
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作者：
L. Moscadelli;Ye Xu;Xi Chen
我们利用跨越约 10 年时间间隔的 7 个 VLBA 观测周期，推导出 CH3OH 12 GHz 脉泽向 W3(OH) 超紧凑 (UC) H ii 区域的精确自行。所达到的速度精度约为 0.1 km s−1 量级，足以精确测量 W3(OH) 中大多数 12 GHz 微波激射器的相对速度，幅度变化范围为 0.3–3 km s−1。朝向 W3(OH)，最强烈的 12 GHz 脉泽集中在 UC H ii 区域北部的一个小区域（北丛）。我们将 CH3OH 12 GHz 微波激射器的自行与从甲醇微波激射器同一区域发射的 OH 6035 MHz 脉射器的自行运动（源自文献数据）进行了比较。在北部团块中，两种脉泽发射从附近（但可能不同）的脉泽气体云中出现，一般来说，视线和天空投影速度的变化相当平滑，这表明两种脉泽类型所追踪的环境和运动学之间存在某种联系。先前提出的锥形流出模型用于解释北部团块中的 12 GHz 脉泽运动学，但无法重现 12 GHz 脉泽自行的新的精确测量结果，因此必须被拒绝。我们重点关注属于“P.A. = 130°–140°线性结构”的北部团块的 12 GHz 微波激射器子集，其 LSR 速度随位置的规律变化为某些有序运动提供了证据。我们证明，考虑到几乎从边缘看的平坦旋转盘，12 GHz 微波激射器的这种“线性分布”的三维速度可以很好地拟合。
We derive accurate proper motions of the CH3OH 12 GHz masers toward the W3(OH) ultra-compact (UC) H ii region, employing seven epochs of VLBA observations spanning a time interval of about 10 yr. The achieved velocity accuracy is of the order of 0.1 km s−1, adequate to precisely measure the relative velocities of most of the 12 GHz masers in W3(OH), with amplitude varying in the range 0.3–3 km s−1. Toward W3(OH), the most intense 12 GHz masers concentrate in a small area toward the north (the northern clump) of the UC H ii region. We have compared the proper motions of the CH3OH 12 GHz masers with those (derived from literature data) of the OH 6035 MHz masers, emitting from the same region of the methanol masers. In the northern clump, the two maser emissions emerge from nearby (but likely distinct) cloudlets of masing gas with, in general, a rather smooth variation of line-of-sight and sky-projected velocities, which suggests some connection of the environments and kinematics traced by both maser types. The conical outflow model, previously proposed to account for the 12 GHz maser kinematics in the northern clump, does not reproduce the new, accurate measurements of 12 GHz maser proper motions and has to be rejected. We focus on the subset of 12 GHz masers of the northern clump belonging to the “linear structure at P.A. = 130°–140°,” whose regular variation of LSR velocities with position presents evidence for some ordered motion. We show that the three-dimensional velocities of this “linear distribution” of 12 GHz masers can be well fitted considering a flat, rotating disk, seen almost edge-on.