AI 中文总结
本研究通过红外样本定量分析发现， bulk ISM运动是大质量恒星弓激波形成与几何形态的主导因素，仅约21%的弓激波为经典恒星驱动型，忽略ISM运动会大幅低估恒星风质量损失率。
AI 中文摘要
弓激波是大质量恒星反馈最常被观测到的影响位点之一，其存在常被视为大质量恒星超音速运动甚至失控性质的证据，弓激波的几何形态也被用于推断恒星风的性质。然而，已有报道显示部分弓激波出现在亚音速大质量恒星周围，或与恒星运动方向取向不同，这表明星际介质（ISM）存在显著影响。本工作定量研究大质量恒星周围弓激波形成的主导原因：从已知弓激波的红外样本出发，测量恒星本动速度与弓激波的对齐程度；结果发现，仅52±2%的弓激波由超音速恒星驱动，70±2%的弓激波存在显著失对准（>30°），样本中仅21±2%的系统可视为由沿恒星运动方向的超音速恒星驱动的经典弓激波，其余79±2%的系统中， bulk ISM运动在激波形成中的作用与恒星运动相当或占主导；随后引入新的统计方法推导需发挥主导作用的ISM运动强度，发现本地静止标准中随机取向的10-15 km s⁻¹级别的ISM运动足以解释样本中弓激波的存在与取向；对于面对HII区的子样本，发现存在来自这些区域的>25 km s⁻¹的外流驱动附近激波的证据；最终结论为，ISM运动是大质量恒星弓激波形成的主导因素，还讨论了忽略这些运动如何导致恒星风质量损失率被低估一个数量级以上。
英文摘要
Bow shocks are one the most commonly observed impact sites of massive star feedback. Their existence is often taken as evidence of the supersonic motion or even runaway nature of the massive star. Bow shock geometry is also used to infer the properties of the stellar wind. However, some bow shocks have been reported around sub-sonic massive stars or are orientated differently than the stellar direction of movement, suggesting a substantial influence of the interstellar medium (ISM). In this work, we quantitatively investigate the dominant cause of bow shock formation around massive stars. Starting from an infrared sample of known bow shocks, we measure the stellar peculiar velocities and degree of alignment of the bow shocks. We find that only half ($52\pm2\%$) of the bow shocks is driven by a supersonic star and that $70\pm2\%$ of bow shocks is substantially misaligned (>30 degrees). Of our sample, only $21\pm2\%$ of systems can be regarded as classical bow shocks, driven by a supersonic star in the direction of stellar movement. For the remaining $79\pm2\%$ of systems, the role of bulk ISM movement in creating the shock is equal to or dominant over the stellar movement. We then introduce a new statistical method to derive the magnitude of the ISM motions required to play this dominant role. We find that ISM motion of the order $10-15$ km s$^{-1}$, oriented randomly within the local standard of rest, suffices to explain the existence and orientations of the bow shocks in our sample. For the subset of systems facing HII regions, we find evidence that outflows at $>25$ km s$^{-1}$ from those regions drive the nearby shocks. We conclude that ISM motion is the dominant factor in creating massive star bow shocks and discuss how ignoring these motions can lead to underestimates of the stellar wind's mass loss rate by more than an order of magnitude.
CommentsAccepted for publication in MNRAS. Links to reproduction package added
