We report the detection of the ordered alignment between the magnetic field and kpc-scale bubbles in the nearby spiral galaxy, NGC 628. Applying the Velocity Gradient Technique on CO spectroscopic data from the ALMA-PHANGS, the magnetic field of NGC 628 is measured at the scale of 191 pc (∼4″). The large-scale magnetic field is oriented parallel to the spiral arms and curves around the galactic bubble structures in the mid-infrared emission observed by the James Webb Space Telescope. A total of 21 bubble structures have been identified at the edges of spiral arms with scales over 300 pc, which includes two kpc-scale structures. These bubbles are caused by supernova remnants and prolonged star formation and are similar to the outflow chimneys found in neutral hydrogen in galactic disks. At the edge of the bubbles, the shocks traced by the O iii emission present a curved magnetic field that parallels the bubble’s shell. The magnetic field follows the bubble expansion and binds the gas in the shell to trigger further star formation. By analyzing the larger sample of 1694 bubbles, we found a distinct radial-size distribution of bubbles in NGC 628 indicating the star formation history in the galaxy.

中文翻译：

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用速度梯度技术测量分子气体的磁场。二. NGC 628 kpc 级气泡中的弯曲磁场


我们报告了对附近螺旋星系 NGC 628 中磁场和 kpc 尺度气泡之间有序排列的检测。对来自 ALMA-PHANGS 的 CO 光谱数据应用速度梯度技术，测量了 NGC 628 的磁场规模为 191 块 (∼4″)。詹姆斯·韦伯太空望远镜观测到的中红外发射中，大尺度磁场的方向与旋臂平行，并围绕星系气泡结构弯曲。在旋臂边缘共发现21个尺度超过300 pc的气泡结构，其中包括2个kpc尺度的结构。这些气泡是由超新星遗迹和长期恒星形成引起的，类似于银河盘中中性氢中发现的流出烟囱。在气泡边缘，O iii 发射所追踪的冲击呈现出与气泡壳平行的弯曲磁场。磁场跟随气泡膨胀并结合壳中的气体以触发进一步的恒星形成。通过分析 1694 个气泡的较大样本，我们发现 NGC 628 中气泡的明显径向尺寸分布表明了星系中的恒星形成历史。