风中诞生的恒星 II：M82晕中的广泛 extraplanar 星形成
Stars Born in the Wind II: Widespread Extra-planar Star Formation in M82's Halo
AI总结：
研究通过HST和Subaru观测揭示M82晕中年轻恒星的分布，发现南弧和东尾的恒星群，表明星流影响及恒星形成历史与盘中星团形成相关。
摘要：
银河系在环境作用下演化——并合和气体流入驱动银河系增长，而超新星引发的银河系流出可能向银河系环境输送气体、金属和能量，从而在远离银河系主体的地方激发恒星形成。通过哈勃空间望远镜（HST）和夏威夷大学超广角相机（Subaru Hyper-Suprime Cam）观测，我们呈现了迄今为止最详细的M82恒星晕中年轻恒星分布图。我们发现广泛分布的extraplanar恒星群，年龄$\lesssim630$ Myr，南弧和东尾的恒星群被清晰检测到，估计过去630 Myr内恒星晕形成总质量约为$\sim4\times10^6\,M_\odot$。整体而言，M82尾的恒星形成历史（SFH）与M82盘中星团形成高峰期相关，表明恒星爆发流出的影响。此外，随着远离M82向东移动，年轻恒星的比例下降。我们提出M82尾由M82向西运动导致的ram压力剥离气体形成，由流出引发的激波触发。
英文摘要：
Galaxies evolve in tandem with their environments -- mergers and gas inflows drive galaxy growth while galactic outflows launched by supernovae may seed the galactic environment with gas, metals, and energy, fueling star-formation far from the main bodies of galaxies. The formation histories of young stars in the stellar halos of nearby galaxies can help understand this interplay. We thus present the most detailed map to date of young stars in the stellar halo of M82, a starburst galaxy in the M81 Group that hosts a prototypical outflow, using Hubble Space Telescope (HST) and Subaru Hyper-Suprime Cam observations. We find widespread extraplanar populations of stars with ages $\lesssim630$ Myr, with clear detections of stars up to $\sim5$ kpc to the south in unique arc-like stellar features (Southern Arcs) and in a new stellar trail up to $\sim20$ kpc to the east (M82's Tail), originating from the Southern Arcs. We estimate a total halo star formation of $\sim4\times10^6\,M_\odot$ in the last $630$ Myr. Overall, the star formation history (SFH) of the M82 Tail is correlated with periods of heightened star cluster formation in the M82 disk, which suggests the influence of the starburst outflow. Further, the fraction of young stars decreases as we move away from M82 to the east. We forward a picture where the M82 Tail formed from ram pressure stripped gas arising from M82's westward motion, triggered by shocks from the outflow.
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