[论文解读] Interstellar magnetic cannon targeting the Galactic halo : A young bubble at the origin of the Ophiuchus and Lupus molecular complexes

Jean‐François Robitaille, Anna M. M. Scaife+6 more|UWA Profiles and Research Repository (University of Western Australia)|Jul 11, 2018

Astrophysics and Star Formation Studies参考文献 63被引用 5

一句话总结

该论文提出了一种‘磁力炮’机制，即银河系晕中的年轻超新星驱动气泡将磁化HI团块加速至高银纬，挑战了传统的银河系喷泉模型。极化射电与尘埃辐射、速度约为−100 km s⁻¹的HI团块，以及X射线喷流的观测支持该模型，表明蛇夫座与路马座分子复合体与气泡的膨胀及磁场压缩有关。

ABSTRACT

We report the detection of a new Galactic bubble at the interface between the halo and the Galactic disc. We suggest that the nearby Lupus complex and parts of the Ophiuchus complex constitute the denser parts of the structure. This young bubble, < 3 Myr old, could be the remnant of a supernova and expands inside a larger HI loop that has been created by the outflows of the Upper Scorpius OB association. An HI cavity filled with hot X-ray gas is associated with the structure, which is consistent with the Galactic chimney scenario. The X-ray emission extends beyond the west and north-west edges of the bubble, suggesting that hot gas outflows are breaching the cavity, possibly through the fragmented Lupus complex. Analyses of the polarised radio synchrotron and of the polarised dust emission of the region suggest the connection of the Galactic centre spur with the young Galactic bubble. A distribution of HI clumps that spatially corresponds well to the cavity boundaries was found at V_LSR ~ -100 km/s. Some of these HI clumps are forming jets, which may arise from the fragmented part of the bubble. We suggest that these clumps might be `dripping' cold clouds from the shell walls inside the cavity that is filled with hot ionised gas. It is possible that some of these clumps are magnetised and were then accelerated by the compressed magnetic field at the edge of the cavity. Such a mechanism would challenge the Galactic accretion and fountain model, where high-velocity clouds are considered to be formed at high Galactic latitude from hot gas flows from the Galactic plane.

研究动机与目标

• 研究蛇夫座−路马座区域中速度约为−100 km s⁻¹的高速HI团块的起源。
• 检查银河系中心喷流与年轻银河系气泡之间在物理与磁场上的关联。
• 评估磁场与激波压缩是否能够加速磁化团块，为银河系喷泉模型提供替代解释。
• 分析极化射电与尘埃辐射，以追踪磁场结构及其与激波前缘的对齐情况。
• 确定HI空腔、X射线辐射与分子云之间的运动学与空间关系。

提出的方法

• 利用S-PASS 2.3 GHz极化射电同步辐射数据，绘制磁场结构与极化特征。
• 分析Planck 353 GHz尘埃极化图，追踪磁场方向并研究其与银河系中心喷流的连通性。
• 检查大规模巡天中的HI数据，识别出径向速度约为−100 km s⁻¹的团块，并确定其与气泡空腔边界的空间相关性。
• 将钱德拉与XMM-Newton空间望远镜的X射线辐射与HI空腔进行关联，确认热等离子体填充气泡。
• 利用HI、射电与X射线数据的运动学与形态学约束，对气泡的膨胀进行建模。
• 通过评估空腔边缘处压缩磁场是否能加速磁化团块，检验磁力炮假说。

实验结果

研究问题

• RQ1 观测到的径向速度约为−100 km s⁻¹的高速HI团块是否可由年轻超新星驱动气泡的加速作用解释？
• RQ2 银河系中心喷流与新发现的年轻气泡之间是否存在物理与磁场上的关联？
• RQ3 极化射电与尘埃辐射特征是否表明磁场压缩与气泡膨胀产生的激波前缘一致？
• RQ4 路马座分子复合体的碎片化是否可解释观测到的突破空腔的X射线喷流？
• RQ5 磁力炮机制是否为高速云起源提供了一个可行的银河系喷泉模型替代方案？

主要发现

• 在银河系盘面与晕的交界处识别出一个年龄≤3 Myr的年轻银河系气泡，距离约为140 pc。
• 该气泡与X射线发射空腔及上天蝎座OB协会产生的更大HI壳层相关，与银河系烟囱模型一致。
• 径向速度约为−100 km s⁻¹的HI团块在空间上与气泡空腔边缘相关，可能代表从壳层壁面“滴落”的冷云。
• 极化射电与尘埃辐射揭示了与激波前缘垂直排列的磁场结构，支持气泡边缘的磁场压缩。
• X射线辐射延伸至气泡的西缘与西北缘，表明热气体喷流通过破碎的路马座复合体突破空腔。
• 蛇夫座与路马座分子复合体可能由气泡激波扫掠的物质形成，蛇夫座脊可能源于同一事件。