Discovery of Linear “Building Blocks” of Water Masers Shaping Linear/Arcuate Microstructures in Cepheus A
Discovery of Linear “Building Blocks” of Water Masers Shaping Linear/Arcuate Microstructures in Cepheus A
复制标题
发现仙王座 A 中形成线性/弓形微结构的水脉泽的线性“构件”
DOI：
10.1086/323061
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发表时间：
2001
期刊：
影响因子：
--
通讯作者：
J. Cantó
中科院分区：
文献类型：
--
作者：
J. Torrelles;N. Patel;José F. Gómez;P. Ho;Luis F. Rodriguez;G. Anglada;G. Garay;L. Greenhill;S. Curiel;J. Cantó
我们报告了三个时期的VLBA水脉泽观测无线电喷流仙王座A HW 2。VLBA的数据显示，以前用VLA探测到的一些脉泽展开成意想不到的和显著的线性/弓形"微观结构"，特别是三个细丝（R1，R2，R3），长度大小为103 - 25 mas（2 - 18 Au），在垂直方向上未分辨一个弧形结构（R4-A），大小为15天文单位（10.1天文单位）;一个弧形脉泽链（R5;我们以前曾报道过），大小为10.10天文单位（10.72天文单位）。这些结构中的一些展开成甚至更小的线性"构建块"（低至0.4 Au的尺度），从而形成"更大"的结构。这些小碎片的扁平外观有力地证明了冲击波的性质。无论是形态和观察到的自行发现在这些水脉泽结构，使我们能够确定至少三个不同的星星形成活动的中心在一个区域的300 mas（200 AU）的投影半径，以前未知的，这可能构成一个三重星星系统。我们认为，R1，R2和R3，这是位于附近的HW 2无线电喷流，但偏离了10200质量相对于其轴，可能起源于由HW 2风在拱星分子气体中挖掘的内部空腔的冲击壁。这意味着与中央HW 2物体相关的广角风的存在。我们还提出，弧形结构R4-A对应于一个未被发现的原恒星（我们预测它位于R4-A的东南方，距离HW 2约200 mas）的风产生的弓形激波结构。最后，这个小区域的第三个能量源可能是激发弧R5的能量源，正如我们之前报道的那样，弧R5正在膨胀，并且与位于HW 2以南10600 mas的一颗身份不明的原恒星有关。这个未知的原星星（~500 Jy）激发的R5弧的水脉泽的通量密度代表了整个仙王座A恒星形成区域的脉泽发射的总通量密度的重要部分（~50%），这表明激发对象可能是一个高质量的星星。此外，我们发现，适合每个历元的R5弧结构的圆的中心，是移动的速度为6公里s-1。这可能是由相关的原星星的自行引起的，因为HW 2和R4-A和R5结构的能量源形成的三重星星系统内的相对轨道运动。
We report three epochs of VLBA water maser observations toward the radio jet Cepheus A HW2. The VLBA data show that some of the masers detected previously with the VLA unfold into unexpected and remarkable linear/arcuate "microstructures," revealing, in particular three filaments (R1, R2, R3) with length sizes ≃3-25 mas (2-18 AU) and unresolved in the perpendicular direction (≲0.1 AU), an arcuate structure (R4-A) of ≃20 mas size (15 AU), and a curved chain of masers (R5; which we have previously reported) of ≃100 mas size (≃72 AU). Some of these structures unfold into even smaller linear "building blocks" (down to scales of 0.4 AU) shaping the "larger" structures. The flattened appearance of these small pieces argues strongly for a shock nature. Both the morphology and the observed proper motions found in these water maser structures have allowed us to identify at least three different centers of star formation activity in a region of ≃300 mas (200 AU) projected radius, unknown previously, and that could constitute a triple star system. We suggest that R1, R2, and R3, which are located close to the HW2 radio jet but offset by ≃200 mas with respect to its axis, could originate at the shocked walls of an inner cavity excavated by the HW2 wind in the circumstellar molecular gas. The presence of a wide-angle wind associated with the central HW2 object is implied. We also propose that the arcuate structure R4-A corresponds to a bow-shock structure produced by the wind of an undetected protostar (which we predict to be located toward the southeast of R4-A, ≃200 mas south from HW2). Finally, the third energy source of this small region could be that one exciting the arc R5, which, as we have previously reported, is expanding and related to an unidentified protostar located ≃600 mas south of HW2. The flux density of the water masers of the R5 arc excited by this unknown protostar (~500 Jy) represents an important fraction (~50%) of the total flux density of the maser emission in the entire Cepheus A star-forming region, suggesting that the exciting object could be a high-mass star. Furthermore, we find that the center of the circle, which fit the R5 arc structure for each epoch, is moving with a velocity of ~6 km s-1. This could be caused by proper motions of the associated protostar because of relative orbital motions within the triple star system formed by HW2 and the energy sources of the R4-A and R5 structures.
影响因子：
3.2
作者：
V. Mannings;A. Boss;S. Russell
通讯作者：
V. Mannings;A. Boss;S. Russell