Near-IR Imaging Polarimetry toward a Bright-rimmed Cloud: Magnetic Field in SFO 74
Near-IR Imaging Polarimetry toward a Bright-rimmed Cloud: Magnetic Field in SFO 74
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针对明亮边缘云的近红外成像偏振测量：SFO 74 中的磁场
DOI：
10.1088/0004-637x/798/1/60
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
Shuji
中科院分区：
文献类型：
--
作者：
Kusune;Takayoshi; Sugitani;Koji; Miao;Jingqi; Tamura;Motohide; Sato;Yaeko; Kwon;Jungmi; Watanabe;Makoto; Nishiyama;Shogo; Nagayama;Takahiro; Sato;Shuji
我们对明亮边缘云(SFO74)进行了近红外(JHK S)成像偏振成像测量。极化矢量图清楚地显示，明亮边缘后面的那一层中的磁场沿着边缘运行，与其周围的磁场有很大不同。尖端边缘后面的磁场方向与入射紫外光的方向几乎垂直，磁场的位形相对于云团对称轴整体上是对称的。利用Chandrasekhar-Fermi方法，我们估计了这两个区域(正好在尖端边缘内部和远离尖端边缘)的列密度和数密度，然后推导出了磁场强度。尖端边缘内部的磁场强度估计为∼90μG，强于远端的∼30μG。这表明，紫外线诱导的激波增强了尖端边缘内部的磁场强度。冲击波增加了尖端周围顶层内的密度，从而增加了磁场的强度。磁场压力似乎与尖端边缘内的湍流压力相当，这意味着磁场对总内压的贡献很大。质通量比估计接近于叶尖边缘内的临界值。我们推测SFO 74的平顶明亮边缘可能是由磁场效应形成的。
We have made near-infrared (JHK s) imaging polarimetry of a bright-rimmed cloud (SFO 74). The polarization vector maps clearly show that the magnetic field in the layer just behind the bright rim is running along the rim, quite different from its ambient magnetic field. The direction of the magnetic field just behind the tip rim is almost perpendicular to that of the incident UV radiation, and the magnetic field configuration appears to be symmetric as a whole with respect to the cloud symmetry axis. We estimated the column and number densities in the two regions (just inside and far inside the tip rim) and then derived the magnetic field strength, applying the Chandrasekhar–Fermi method. The estimated magnetic field strength just inside the tip rim,∼ 90 μG, is stronger than that far inside,∼ 30 μG. This suggests that the magnetic field strength just inside the tip rim is enhanced by the UV-radiation-induced shock. The shock increases the density within the top layer around the tip and thus increases the strength of the magnetic field. The magnetic pressure seems to be comparable to the turbulent one just inside the tip rim, implying a significant contribution of the magnetic field to the total internal pressure. The mass-to-flux ratio was estimated to be close to the critical value just inside the tip rim. We speculate that the flat-topped bright rim of SFO 74 could be formed by the magnetic field effect.