Two-component Magnetic Field along the Line of Sight to the Perseus Molecular Cloud: Contribution of the Foreground Taurus Molecular Cloud
Two-component Magnetic Field along the Line of Sight to the Perseus Molecular Cloud: Contribution of the Foreground Taurus Molecular Cloud
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DOI：
10.3847/1538-4357/abfcc5
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发表时间：
2021-04
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通讯作者：
Y. Doi;T. Hasegawa;P. Bastien;M. Tahani;D. Arzoumanian;S. Coud'e;M. Matsumura;S. Sadavoy;C. H
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作者：
Y. Doi;T. Hasegawa;P. Bastien;M. Tahani;D. Arzoumanian;S. Coud'e;M. Matsumura;S. Sadavoy;C. H
在英仙座分子云方向的光学恒星偏振测量显示出一个完全混合的双峰分布的位置角在整个云。我们研究了盖亚三角距离这些恒星，并揭示了两个组件的位置角跟踪两个不同的尘埃云沿着视线。其中一个分量的偏振角为−37.°6 ± 35.°2，偏振率更高，为2.0 ± 1.7%，主要追踪英仙座分子云，距离为300 pc。另一个分量的偏振角为+66. ° 8 ± 19.°1，偏振率较低，为0.8 ± 0.6%，它跟踪的是距离为150 pc的前景云。前景云是暗淡的，最大的视觉消光≤1马格。我们确定，前景云的金牛座分子云的外缘。在英仙座和金牛座分子云之间，我们发现了一个密度较低的椭球形尘埃腔，大小为100-160 pc。这个尘埃腔位于l = 170°，B = −20°，d = 240 pc，这对应于通常与Per OB 2关联的HI壳层。因此，观测到的英仙座分子云的双分量偏振特征可以用这个尘埃腔前部和后部磁场的天平面方向的组合来解释。
Optical stellar polarimetry in the Perseus molecular cloud direction is known to show a fully mixed bimodal distribution of position angles across the cloud. We study the Gaia trigonometric distances to each of these stars and reveal that the two components in position angles trace two different dust clouds along the line of sight. One component, which shows a polarization angle of −37.°6 ± 35.°2 and a higher polarization fraction of 2.0 ± 1.7 %, primarily traces the Perseus molecular cloud at a distance of 300 pc. The other component, which shows a polarization angle of +66.°8 ± 19.°1 and a lower polarization fraction of 0.8 ± 0.6 %, traces a foreground cloud at a distance of 150 pc. The foreground cloud is faint, with a maximum visual extinction of ≤1 mag. We identify that foreground cloud as the outer edge of the Taurus molecular cloud. Between the Perseus and Taurus molecular clouds, we identify a lower-density ellipsoidal dust cavity with a size of 100–160 pc. This dust cavity is located at l = 170°, b = −20°, and d = 240 pc, which corresponds to an HI shell generally associated with the Per OB2 association. The two-component polarization signature observed toward the Perseus molecular cloud can therefore be explained by a combination of the plane-of-sky orientations of the magnetic field both at the front and at the back of this dust cavity.