标题： 缓慢移动恒星周围的电离氢区内的风泡 显示英文标题

标题： Wind bubbles within H II regions around slowly moving stars

摘要： 围绕O型恒星的星际气泡是由恒星的风和电离辐射共同驱动的。 风的贡献不确定，因为风与星际介质之间的边界难以观测。 中红外观测（例如，对H II区RCW 120的观测）显示了O型恒星周围的尘埃发射弧线，这些弧线很好地局限在H II区的气泡内部。 这些弧线可能指示了一个不对称的恒星风气泡的边缘，该气泡因密度梯度和/或恒星运动而发生扭曲。 我们提出了二维辐射流体动力学模拟，研究了在密集（n=3000 cm^{-3}）、均匀的介质中以4到16 km/s速度移动的大质量恒星周围的风泡和H II区的演化。 正如预期的那样，H II区形态强烈受到恒星运动的影响，但风泡从出生起就非常非球形，即使对于考虑的最低空间速度也是如此。 风泡不会充满它们的H II区（我们发现填充因子为10-20%），至少对于质量M~30 Msun的主序星来说是这样。 此外，即使对于超音速速度，风弓激波也不会显著捕获电离前沿。 风泡的X射线辐射较软、较弱，并且主要来自风泡与H II区之间的湍流混合层。 风泡在X射线中的能量辐射不到1%；它通过与较冷的光致电离气体的湍流混合损失了大部分能量。 将模拟结果与H II区RCW 120进行比较表明，其动力学年龄<=0.4 Myr，并且恒星运动<=4 km/s是允许的，这意味着电离源不太可能是逃逸星，而更有可能是在原地形成的。 该区域的年轻性和与其他O型或B型恒星的明显隔离性使其成为大质量恒星形成和初始质量函数研究的非常有趣的目标。 显示英文摘要

摘要： Interstellar bubbles around O stars are driven by a combination of the star's wind and ionizing radiation output. The wind contribution is uncertain because the boundary between the wind and interstellar medium is difficult to observe. Mid-infrared observations (e.g., of the H II region RCW 120) show arcs of dust emission around O stars, contained well within the H II region bubble. These arcs could indicate the edge of an asymmetric stellar wind bubble, distorted by density gradients and/or stellar motion. We present two-dimensional, radiation-hydrodynamics simulations investigating the evolution of wind bubbles and H II regions around massive stars moving through a dense (n=3000 cm^{-3}), uniform medium with velocities ranging from 4 to 16 km/s. The H II region morphology is strongly affected by stellar motion, as expected, but the wind bubble is also very aspherical from birth, even for the lowest space velocity considered. Wind bubbles do not fill their H II regions (we find filling factors of 10-20%), at least for a main sequence star with mass M~30 Msun. Furthermore, even for supersonic velocities the wind bow shock does not significantly trap the ionization front. X-ray emission from the wind bubble is soft, faint, and comes mainly from the turbulent mixing layer between the wind bubble and the H II region. The wind bubble radiates <1 per cent of its energy in X-rays; it loses most of its energy by turbulent mixing with cooler photoionized gas. Comparison of the simulations with the H II region RCW 120 shows that its dynamical age is <=0.4 Myr and that stellar motion <=4 km/s is allowed, implying that the ionizing source is unlikely to be a runaway star but more likely formed in situ. The region's youth, and apparent isolation from other O or B stars, makes it very interesting for studies of massive star formation and of initial mass functions.