The Spatio-Kinematical Structure and Distance of the Preplanetary Nebula IRAS 19134+2131
The Spatio-Kinematical Structure and Distance of the Preplanetary Nebula IRAS 19134+2131
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DOI：
10.1086/521350
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发表时间：
2007-07
期刊：
影响因子：
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通讯作者：
H. Imai;R. Sahai;M. Morris
中科院分区：
文献类型：
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作者：
H. Imai;R. Sahai;M. Morris
我们利用甚长基线天线阵观测了行星际前星云IRAS 19134+2131（I19134）中的H2O脉泽发射，其中H2O脉泽谱具有两组径向速度相距约100 km/s的特征。我们还利用哈勃太空望远镜获得了I19134的光学图像，首次定位了该源中的双极反射星云。H2 O脉泽的空间运动学结构表明，存在一个快速的平行旋进流，其在天平面上的投影范围约为140 mas，膨胀速率约为1.9mas/yr，动力学年龄仅为40 yr。两个检测到的光学波瓣也在与准直流的方向几乎相同的方向上分离约150质量。水脉泽外流和光学瓣的范围和方向之间的良好协议表明，最近形成的瓣沿着准直快流。因此，围绕演化星星的星周包层显然已被快速流穿透，并已被清除，以便在快速流的方向上出现星光。在一年多的时间里，我们测量了所有被探测到的脉泽特征相对于河外参考源J1925+2106的位置。因此，我们分析了脉泽特征运动，包括组合的年度视差，长期运动银河系旋转，和内流的运动。我们得到了I19134的年视差距离D = 8.0 kpc，并估计它在银河系中的位置为（R，θ，z）=（7.4 kpc，62° ± 5°，0.65 kpc）。根据脉泽团的蓝移和红移平均运动，我们估计I19134的三维长期运动为（VR，Vθ，Vz）=（3，125，8）km s-1.从银河平面的高度z和垂直于银河平面的速度分量Vz，我们估计I19134的恒星质量的大致上限为9 M。
Using the Very Long Baseline Array at six epochs, we have observed H2O maser emission in the preplanetary nebula IRAS 19134+2131 (I19134), in which the H2O maser spectrum has two groups of emission features separated in radial velocity by ~100 km s-1. We also obtained optical images of I19134 with the Hubble Space Telescope to locate the bipolar reflection nebula in this source for the first time. The spatio-kinematical structure of the H 2O masers indicates the existence of a fast, collimated (precessing) flow having a projected extent of ~140 mas and an expansion rate of ~1.9 mas yr-1 on the sky plane, which gives a dynamical age of only ~40 yr. The two detected optical lobes are also separated by ~150 mas in almost the same direction as that of the collimated flow. The good agreement between the extent and orientation of the H2O maser outflow and optical lobes suggests that the lobes have been recently formed along the collimated fast flow. Thus, the circumstellar envelope around the evolved star has apparently been penetrated by the fast flow and has been cleared for the emergence of the starlight in the directions of the fast flow. The positions of all of the detected maser features have been measured with respect to the extragalactic reference source J1925+2106 over one year. Therefore, we analyzed maser feature motions that consist of the combination of an annual parallax, a secular motion following Galactic rotation, and the intrinsic motions within the flow. We obtain an annual-parallax distance to I19134 of D = 8.0 kpc and estimate its location in the Galaxy to be (R, θ, z) = (7.4 kpc, 62° ± 5°, 0.65 kpc). From the mean motion of the blueshifted and redshifted clusters of maser features, we estimate the three-dimensional (3D) secular motion of I19134 to be (VR,Vθ,Vz) = (3, 125, 8) km s-1. From the height from the Galactic plane, z, and the velocity component perpendicular to the Galactic plane, Vz, we estimate a rough upper limit of ~9 M☉ to the stellar mass of I19134's progenitor.