The far distance to G7.47+0.06 from proper motion measurement of H2O masers
The far distance to G7.47+0.06 from proper motion measurement of H2O masers
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DOI：
10.1093/pasj/psw058
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发表时间：
2016-08
影响因子：
2.3
通讯作者：
Aya Yamauchi;K. Yamashita;M. Honma;K. Sunada;A. Nakagawa;Y. Ueno
中科院分区：
文献类型：
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作者：
Aya Yamauchi;K. Yamashita;M. Honma;K. Sunada;A. Nakagawa;Y. Ueno
我们报道了利用VLBI射电天体探测技术对与超紧凑的HⅡ区G7.47+0.06有关的22 GHz H_2O脉泽特征的距离测量。由于震源的距离超过10kpc，因此很难从每年的视差测量中得出该距离。与此同时，我们清楚地探测到了震源平行于银河系平面的自行运动。自行为μ=−5.03±0.07ma yr−1，正在接近银河系中心。我们应用了一种基于绝对自行的新方法来确定震源距离。考虑到银河系自转曲线的不确定性和太阳的特殊运动，探测到的自行导致震源距离D=20±2kpc，这表明，即使对于距离太远而无法测量年视差的震源，天文观测也可以提供10%的精确距离测量。最后，我们将前文中估计的HⅡ区的物理参数定为20kpc，并表明H2O脉泽特征与一个与O5.5光谱类型相对应的大质量恒星形成区有关。
We report on a distance measurement of 22 GHz H 2 O maser features associated with an ultra-compact H II region G7.47 + 0.06 using VERA (VLBI Exploration of Radio Astrom-etry). Since the source is located farther away than 10 kpc, it turned out to be difficult to derive the distance from annual parallax measurement. Meanwhile, we clearly detected the source’s proper motion parallel to the Galactic plane. The proper motion is μ = − 5.03 ± 0.07 mas yr − 1 and is approaching the Galactic center. We applied a new method to determine the source distance based on absolute proper motions. Considering uncertainties of the Galactic rotation curve and the solar peculiar motion, the detected proper motion leads to a source distance of D = 20 ± 2 kpc, demonstrating that astrometric observation can provide an accurate distance measurement at a 10% level even for sources too distant to measure the annual parallax. Lastly, we scale the physical parameters of the H II region estimated in a previous paper to be 20 kpc, and show that the H 2 O maser features are associated with a massive star-forming region corresponding to the spectral type of O5.5.