标题： 行星状星云中的高速区域 显示英文标题

标题： High-velocity regions in planetary nebulae

摘要： 研究行星状星云的内部速度场，分辨率为 5 公里每秒$^{-1}$。 我们分析了来自 Bulge、人马矮星系和大麦哲伦云（SMC）中的三个星云的深级联光谱。 除了中央恒星快速风可能较慢开始外，未发现金属丰度的影响。 发现了高能冲击波存在于星云内边缘的有力证据。 这种冲击波在流体力学模型中被预测，但之前从未被观测到。 冲击波气体由中央恒星的快速风加速。 在外缘类似的冲击波追踪电离壳层向外膨胀进入周围的渐近红巨星（AGB）风。 还从两个星云的中间激发线中发现了局部高能区域的证据。 我们探讨了几种可能的解释： (1) 在扫过内壳外缘位置的流体力学模型预测的中间半径处嵌入的冲击； (2) 偏离球对称性，在某些方向上中间激发线延伸到外冲击区域； (3) 在一些银河系行星状星云中看到的中间扫过的壳层。 剩下的具有[WC]星的星云显示出强烈的湍流。 这可能追踪许多嵌入的小型冲击。 我们建议与时间变化的[WC]风有关，这使行星状星云受到多种声波影响。 显示英文摘要

摘要： The internal velocity fields of planetary nebulae are studied with a resolution of 5 km s$^{-1}$. We analyze deep echelle spectra from three nebulae in the Bulge, the Sagittarius Dwarf and the SMC. No effects of metallicity is seen, except possibly a slower onset of the fast wind from the central star. Robust evidence is found for the existence of a high-velocity shock at the inner edges of the nebulae. Such a shock is predicted in hydrodynamical models but had not previously been observed. The shock gas is accelerated by the fast wind from the central star. A similar shock at the outer edges traces the expansion of the ionized shell into the ambient AGB wind. Evidence for localized regions of high velocity is also found from lines of intermediate excitation, for two of nebulae. We explore several possible interpretations: (1) an embedded shock at intermediate radii, as predicted by hydrodynamic models at the position of the outer edge of the swept-up inner shell; (2) deviations form spherical symmetry, where in some directions the intermediate-excitation lines extend into the region of the outer shock; (3) An intermediate swept-up shell, as seen in some Galactic planetary nebulae. The remaining nebula, with a [WC] star, shows strong turbulence. This may trace a superposition of many embedded shock-lets. We suggest a relation to the time-variable [WC] wind, giving a planetary nebula subjected to a multitude of sound waves.