猎户座-波江座超气泡中的气壳层和磁场
Gas shells and magnetic fields in the Orion-Eridanus superbubble
摘要：
猎户座-波江座超级气泡是由猎户座OB星协中大质量恒星的超新星和超音速风吹来的。超级泡沫的形成历史和当前结构仍然知之甚少。它可能由沿视线嵌套的壳的组合组成。我们利用原子分子气体的一种新的分解方法研究了超泡波江座一侧的复合结构。我们使用HI和CO发射线分离相干气体壳在空间和速度，我们研究了它们的关系，温暖的电离气体探测H $α$发射，热等离子体发射X射线，和跟踪尘埃极化发射的磁场。我们还使用尘埃红化图和X射线吸收来限制到云层的相对距离。我们使用尘埃极化数据来估计几个云和超级气泡外缘的磁场的天空平面分量。我们的气体分解揭示了超级气泡内部的几个外壳，它们的距离从150 pc到250 pc不等。其中一个壳形成了一个几乎完整的环，充满了热等离子体。其他壳层可能对应于在膨胀的外激波后面被压缩的扫掠气体层。我们利用激波下游的气体和磁场数据得出了接近20 km/s的激波膨胀速度。考虑到气体对X射线的吸收，我们发现超泡内部的热等离子体的压强超过了局域泡。它包括沿着视线的较热（3-9 MK）和较冷（0.3-1.2 MK）气体的混合物。沿着西部和南部边缘以及在超级气泡的接近壁中的磁场似乎被正在进行的膨胀所塑造和压缩。我们发现，沿边缘的天空平面磁场强度范围从3到15 $μ$ G。
英文摘要：
The Orion-Eridanus superbubble has been blown by supernovae and supersonic winds of the massive stars in the Orion OB associations. The formation history and current structure of the superbubble are still poorly understood. It possibly consists of a combination of nested shells along the line of sight. We have investigated the composite structure of the Eridanus side of the superbubble in the light of a new decomposition of the atomic and molecular gas. We used HI and CO emission lines to separate coherent gas shells in space and velocity, and we studied their relation to the warm ionised gas probed in H$α$ emission, to the hot plasma emitting X-rays, and to the magnetic fields traced by dust polarised emission. We also constrained the relative distances to the clouds using dust reddening maps and X-ray absorption. We used the dust polarisation data to estimate the plane-of-sky components of the magnetic field in several clouds and along the outer rim of the superbubble. Our gas decomposition has revealed several shells inside the superbubble that span distances from about 150 pc to 250 pc. One of these shells forms a nearly complete ring filled with hot plasma. Other shells likely correspond to the layers of swept-up gas that is compressed behind the expanding outer shock wave. We used the gas and magnetic-field data downstream of the shock to derive a shock expansion velocity close to 20 km/s. Taking the X-ray absorption by the gas into account, we find that the pressure of the hot plasma inside the superbubble exceeds that in the Local Bubble. It comprises a mix of hotter (3-9 MK) and cooler (0.3-1.2 MK) gas along the lines of sight. The magnetic field along the western and southern rims and in the approaching wall of the superbubble appears to be shaped and compressed by the ongoing expansion. We find plane-of-sky magnetic strengths ranging from 3 to 15 $μ$G along the rim.
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