The Explosion in Orion-KL as Seen by Mosaicking the Magnetic Field with ALMA
The Explosion in Orion-KL as Seen by Mosaicking the Magnetic Field with ALMA
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DOI：
10.3847/1538-4357/abcafb
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发表时间：
2020-11
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通讯作者：
P. Cortés;Valentin J. M. Le Gouellec;C. Hull;J. Girart;F. Louvet;E. Fomalont;S. Kameno;G. Moellenbrock;H. Nagai;K. Nakanishi;E. Villard
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作者：
P. Cortés;Valentin J. M. Le Gouellec;C. Hull;J. Girart;F. Louvet;E. Fomalont;S. Kameno;G. Moellenbrock;H. Nagai;K. Nakanishi;E. Villard
我们提出了由阿塔卡马大型毫米/亚毫米阵列（ALMA）进行的第一次线偏振拼接观测。作为ALMA扩展和优化能力计划的一部分，我们使用3.1和1.3毫米的超采样马赛克绘制了猎户座- kleinmann - low（猎户座- kl）星云。我们通过假设尘埃颗粒相对于环境磁场排列，推导出天空平面上的磁场形态。在星云的中心，我们发现了一个准径向磁场模式，它与爆炸CO流出物对齐，半径约为12″（~ 5000 au），超过这个模式平滑地过渡到准沙漏形状，类似于詹姆斯-克拉克-麦克斯韦望远镜（JCMT）在更大规模观测中看到的形态。我们估计平均磁场强度为mG，总磁能为2 × 1045 erg，比爆炸CO流出的能量小3个数量级。我们得出结论，该场已经被流出物淹没，并且激波正在从星云中心传播，在距离爆炸中心约5000 au的磁力线中可以看到激波锋面。
We present the first linear-polarization mosaicked observations performed by the Atacama Large Millimeter/submillimeter Array (ALMA). We mapped the Orion-KLeinmann-Low (Orion-KL) nebula using super-sampled mosaics at 3.1 and 1.3 mm as part of the ALMA Extension and Optimization of Capabilities program. We derive the magnetic field morphology in the plane of the sky by assuming that dust grains are aligned with respect to the ambient magnetic field. At the center of the nebula, we find a quasi-radial magnetic field pattern that is aligned with the explosive CO outflow up to a radius of approximately 12″ (∼5000 au), beyond which the pattern smoothly transitions into a quasi-hourglass shape resembling the morphology seen in larger-scale observations by the James-Clerk-Maxwell Telescope (JCMT). We estimate an average magnetic field strength mG and a total magnetic energy of 2 × 1045 erg, which is three orders of magnitude less than the energy in the explosive CO outflow. We conclude that the field has been overwhelmed by the outflow and that a shock is propagating from the center of the nebula, where the shock front is seen in the magnetic field lines at a distance of ∼5000 au from the explosion center.