盘状星系中Halpha截止的一种自然解释的反常恒星形成
Clustered star formation as a natural explanation of the Halpha cutoff in disc galaxies
摘要：
恒星的形成主要取决于对H $α$辐射的观测，这与短寿命大质量恒星的存在有关。盘状星系在一定的银河系中心距离上显示出H $α$辐射的强截止，这导致了在盘状星系的外部区域恒星形成被抑制的结论。这似乎与最近的紫外线观测相矛盾（Boissier等人，2007），这意味着盘星系有恒星形成超过Halpha截止，恒星形成表面密度与底层气体表面密度线性相关，比Halpha光度（Kennicutt，1998）更浅。在一个星系范围的公式中，恒星形成的集群性质最近导致了这样一种见解，即星系总的H α光度与星系范围的恒星形成率非线性相关（Pflamm-Altenburg等人，2007年d）。在这里，我们表明，一个地方制定的概念，集群恒星形成自然会导致一个陡峭的径向下降的Halpha表面光度比恒星形成率表面密度的定量协议的意见，并观察到的Halpha截止自然产生。
英文摘要：
Star formation is mainly determined by the observation of H$α$ radiation which is related to the presence of short lived massive stars. Disc galaxies show a strong cutoff in H$α$ radiation at a certain galactocentric distance which has led to the conclusion that star formation is suppressed in the outer regions of disc galaxies. This is seemingly in contradiction to recent UV observations (Boissier et al., 2007) that imply disc galaxies to have star formation beyond the Halpha cutoff and that the star-formation-surface density is linearly related to the underlying gas surface density being shallower than derived from Halpha luminosities (Kennicutt, 1998). In a galaxy-wide formulation the clustered nature of star formation has recently led to the insight that the total galactic Halpha luminosity is non-linearly related to the galaxy-wide star formation rate (Pflamm-Altenburg et al., 2007d). Here we show that a local formulation of the concept of clustered star formation naturally leads to a steeper radial decrease of the Halpha surface luminosity than the star-formation-rate surface density in quantitative agreement with the observations, and that the observed Halpha cutoff arises naturally.
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