He II emission in extragalactic H II regions
He II emission in extragalactic H II regions
复制标题
河外 H II 区域的 He II 发射
DOI：
10.1086/170065
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发表时间：
1991
期刊：
影响因子：
--
通讯作者：
E. Skillman
中科院分区：
文献类型：
--
作者：
D. Garnett;R. Kennicutt;Y. Chu;E. Skillman
光谱观测证实了 SMC H II 区域 N76 中存在星云 He II 4686-A 发射，并证明与 IC 1613 中的 WO 星相关的 He II 发射也得到了扩展。讨论了四个 H II 区域的特性。发射与特定恒星的密切相关性表明恒星本身的光电离是激发机制，并且提出对于那些被WO星电离的星云和一些罕见的高激发WN星来说这可能是正确的。这些带有 He II 发射的星云的存在增加了在矮发射线星系中经常观察到的 4686-A 发射起源于星云的可能性。这得出了这样的结论：与恒星形成区域相关的辐射场可能比之前猜测的更难，并重新提出了年轻星系中恒星的光电离是否可以解释 QSO 吸收线系统中观察到的电离的问题。 42 参考文献
Spectroscopic observations confirming the presence of nebular He II 4686-A emission in the SMC H II region N76 are presented, and it is demonstrated that the He II emission associated with the WO star in IC 1613 is also extended. The properties of four H II regions are discussed. The close correlation of the emission with specific stars indicates that photoionization by the stars themselves is the excitation mechanism, and it is proposed that this may be true for those nebulae ionized by WO stars and some rare high-excitation WN stars. The existence of these nebulae with He II emission increases the likelihood that the 4686-A emission frequently observed in dwarf emission-line galaxies is nebular in origin. This prompts the conclusion that the radiation field associated with star-forming regions can be harder than previously suspected, and reopens the issue of whether photoionization by stars in young galaxies can account for the ionization observed in QSO absorption-line systems. 42 refs.