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arXiv 2109.13670astro-ph.GA
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超新星遗迹W44的磁场层析成像

Velocity Gradients: Magnetic Field Tomography towards the Supernova Remnant W44

Mingrui Liu, Yue Hu, Alex Lazarian

摘要:

速度梯度技术(VGT)作为一种新的星际磁场追踪方法,已被证明是探测扩散星际介质(ISM)中磁场的有效方法。在这项工作中,我们验证了VGT在更广泛的背景下,通过将该技术应用到与超新星遗迹(SNR)W44相互作用的分子云。我们用CO、$\rm HCO^+$和H I发射线探测了VGT的磁场,并与普朗克353 GHZ尘埃极化进行了比较。我们表明,VGT给出了一个准确的测量,尤其是在激烈的分子气体发射区的普朗克极化相干。我们进一步研究了前景的贡献,导致在低强度分子气体领域的VGT和普朗克测量之间的错位的偏振。我们改进了VGT,通过将W44分解为各种速度分量来实现磁场层析成像。我们发现,W44的速度分量在$v\sim45$公里的$^{-1}$表现出最大的覆盖范围,并给出了最好的协议与普朗克极化的磁场方向。

英文摘要:

As a novel approach for tracing interstellar magnetic fields, the Velocity Gradient Technique (VGT) has been proven to be effective for probing magnetic fields in the diffuse interstellar medium (ISM). In this work, we verify the VGT in a broader context by applying the technique to a molecular cloud interacting with the supernovae remnant (SNR) W44. We probe the magnetic fields with the VGT using CO, $\rm HCO^+$, and H I emission lines and make a comparison with the Planck 353 GHZ dust polarization. We show that the VGT gives an accurate measurement that coheres with the Planck polarization especially in intense molecular gas emission regions. We further study the foreground's contribution to the polarization that results in a misalignment between the VGT and the Planck measurements in low-intensity molecular gas areas. We advance the VGT to achieve magnetic field tomography by decomposing the W44 into various velocity components. We show that W44's velocity component at $v\sim45$ km s$^{-1}$ exhibits the largest coverage and gives the best agreement with Planck polarization in terms of magnetic field orientation.

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