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arXiv 2007.12180astro-ph.GAastro-ph.EPastro-ph.HEastro-ph.SR
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局部星际环境的形成和演化：核合成和X射线数据的联合约束

Formation and evolution of the local interstellar environment: combined constraints from nucleosynthetic and X-ray data

Yusuke Fujimoto, Mark R. Krumholz, Shu-ichiro Inutsuka, Alan P. Boss, Larry R. Nittler

备注：
7 pages, 5 figures. Accepted for publication in MNRAS
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摘要：

一些观测结果表明，太阳系位于一个受到大质量恒星反馈影响的区域至少有几百万年的历史;这些观测结果包括在深海档案和南极雪中探测到了活跃的$^{60}\text{Fe}$，在全天空$γ$射线图中看到的银河平面周围的$^{60}\text{Fe}$广泛的角分布，以及全天空的软X射线背景。然而，我们在银河系圆盘内的位置使我们很难完全了解这个环境，而且我们有限的时间基线无法提供有关其形成历史或与大规模银河系动力学关系的信息。我们探索这些问题，通过使用$N$体+流体动力学模拟的银河系，以确定恒星的太阳一样的轨道上，其环境将产生的条件与我们观察到的一致。我们发现这样的恒星并不常见，但也不是特别罕见。这些恒星被发现主要是在螺旋臂的边缘附近，并躺在kpc尺度的气泡，这些气泡是由多代恒星形成的手臂。我们调查了恒星的轨迹，发现在气泡中停留的时间范围从20万年到90万年。持续时间取决于恒星穿过旋臂的时间，通常短于气泡的寿命，气泡的寿命是$\sim 100$ Myr，这是旋臂环境提供持续气体供应的结果。

英文摘要：

Several observations suggest that the Solar system has been located in a region affected by massive stellar feedback for at least a few Myr; these include detection of live $^{60}\text{Fe}$ in deep-sea archives and Antarctic snow, the broad angular distribution of $^{26}\text{Al}$ around the Galactic plane seen in all-sky $γ$-ray maps, and the all-sky soft X-ray background. However, our position inside the Galactic disc makes it difficult to fully characterise this environment, and our limited time baseline provides no information about its formation history or relation to large-scale Galactic dynamics. We explore these questions by using an $N$-body+hydrodynamics simulation of a Milky-Way-like galaxy to identify stars on Sun-like orbits whose environments would produce conditions consistent with those we observe. We find that such stars are uncommon but not exceptionally rare. These stars are found predominantly near the edges of spiral arms, and lie inside kpc-scale bubbles that are created by multiple generations of star formation in the arm. We investigate the stars' trajectories and find that the duration of the stay in the bubble ranges from 20 Myr to 90 Myr. The duration is governed by the crossing time of stars across the spiral arm. This is generally shorter than the bubble lifetime, which is $\sim 100$ Myr as a result of the continuous gas supply provided by the arm environment.

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