Internal Proper Motions of Methanol Masers at 6.7GHz in Massive Star-Forming Region Onsala 1
Internal Proper Motions of Methanol Masers at 6.7GHz in Massive Star-Forming Region Onsala 1
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DOI：
10.1093/pasj/63.1.53
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发表时间：
2011-02
影响因子：
2.3
通讯作者：
K. Sugiyama;K. Fujisawa;A. Doi;M. Honma;Y. Isono;H. Kobayashi;N. Mochizuki;Y. Murata;S. Sawada-Sato
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文献类型：
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作者：
K. Sugiyama;K. Fujisawa;A. Doi;M. Honma;Y. Isono;H. Kobayashi;N. Mochizuki;Y. Murata;S. Sawada-Sato
我们用日本甚长基线干涉测量网络(JVN)测量了大质量恒星形成区Onsala 1(On 1)中6.7 GHz甲醇脉泽的内部自身运动，时间跨度为778天。甲醇脉泽与水脉泽明显不同。甲醇脉泽围绕着一个超致密的(UC)H II区，其分布类似于羟基脉泽。甲醇脉泽的内部运动被清晰地探测到，它们大致呈南北向外运动，相对速度为�5km S�1。它们的运动类似于羟基脉泽，后者在�5km S�1处表现为扩张，这两种脉泽似乎追踪着正在扩张的UC H II区。另一种可能性是甲醇脉泽与H13CO+和SiO谱线观察到的分子外流有关，因为甲醇脉泽的方向和速度与分子谱线的方向和速度相似。对于大质量年轻星体演化阶段水脉泽和甲醇脉泽的相对位相，通过比较脉泽的位置，我们发现水脉泽早于1中的甲醇脉泽。水脉泽与亚毫米波长的尘埃发射有关，而甲醇脉泽与厘米波长的UC H II区有关，后者出现在比尘埃核心更晚的演化阶段。
We present the internal proper motions of 6.7 GHz methanol masers in a massive star-forming region, Onsala 1 (ON 1), measured using the Japanese very long baseline interferometry network (JVN) at three epochs spanning 778 days. The methanol masers were clearly distinct from water masers. The methanol masers surrounded an ultracompact (UC) H II region, and their distribution was similar to that of hydroxyl masers. The internal motions of the methanol masers were clearly detected; they show outward motions in roughly the north–south direction with a relative velocity of � 5k m s � 1 . Their motion is similar to that of hydroxyl masers, which showed expansion at � 5k m s � 1 , and these two types of masers seem to trace the expanding UC H II region. Another possibility is that the methanol masers are associated with a molecular outflow observed by H 13 CO + and SiO lines, because the direction and velocity of the methanol masers were similar to those of the molecular lines. Regarding the relative phases of water and methanol masers in the evolutionary stage of massive young stellar objects, we found that the former was earlier than the latter in ON 1 by comparing the sites associated with the masers. The water masers were associated with dust emission at submillimeter wavelengths, whereas the methanol masers were associated with an UC H II region at centimeter wavelengths, which appears at a later evolutionary phase than the dust core.