The origin of strong nebular HeII emission at low and high redshift

最近对高红移的观测显示出非常高的电离星云线，类似的线在低红移星系中非常罕见，并且大多与热的、演化的沃尔夫-拉叶星有关。现在看来，只有极少数的本星系存在，它们显示出这样的高度电离的星云线，而没有沃尔夫-拉叶星的特征。我们建议研究这些潜在的本地类似的高度电离的年轻星系，以更好地了解这些线的电离机制。这将有助于澄清，如果观察到的高电离线在一些高红移星爆（原）星系确实是由极端贫金属，非常大质量的恒星的辐射场。

Recent observations of high redshift show very high ionized nebular lines Similar lines are extremely rare in low redshift galaxies and there mostly connected to hot, evolved Wolf-Rayet stars. Now it appears that a very small number of localgalaxies exist, which show such highly ionized nebular lines without signatures of Wolf-Rayet stars. We propose to study these potential local analogs to the highly ionized young galaxies in order to better understand the ionization mechanisms of these lines. This will allow to clarify, if the observed high-ionization lines in some high redshift starbursts (proto-)galaxies are indeed created by the radiation field of extremely metal-poor, very massive stars.