将Halpha光度转换为SFR
Converting Halpha luminosities into SFRs
摘要：
星系的恒星形成率（SFR）通常是通过将测量的H α光度（L_H α）转换成当前的SFR来计算的。该转换基于与总SFR无关的恒定初始质量函数（IMF）。正如最近所认识到的，星团中的最大恒星质量受到嵌入星团总质量的限制，此外，最大嵌入星团质量受到当前SFR的限制。这两个关系的组合导致一个完整的银河系初始恒星质量函数（IGIMF，IMF为整个星系），这是陡峭的高质量制度比恒定的正则IMF，并依赖于SFR的星系。因此，L_Halpha-SFR关系变为非线性的，并且对于低SFR而言是非线性的。特别是对于矮星系，SFR可以被低估三个数量级。我们修改现有的线性L_Halpha-SFR关系使用我们的IGIMF概念。这些可能会导致宇宙学恒星形成历史的修订。我们还表明，在雕塑家矮不规则星系的IGIMF形式主义的情况下，意味着总SFR的总星系气体质量的线性依赖。一个恒定的气体耗尽时间尺度的几个陀螺仪的结果独立的星系气体质量与减少散射相比，传统的结果。我们的研究结果是定性独立的明确选择的IGIMF的细节和挑战目前的恒星形成理论在矮星系。
英文摘要：
Star-formation rates (SFRs) of galaxies are commonly calculated by converting the measured Halpha luminosities (L_Halpha) into current SFRs. This conversion is based on a constant initial mass function (IMF) independent of the total SFR. As recently recognised the maximum stellar mass in a star cluster is limited by the embedded total cluster mass and, in addition, the maximum embedded star cluster mass is constrained by the current SFR. The combination of these two relations leads to an integrated galaxial initial stellar mass function (IGIMF, the IMF for the whole galaxy) which is steeper in the high mass regime than the constant canonical IMF, and is dependent on the SFR of the galaxy. Consequently, the L_Halpha-SFR relation becomes non-linear and flattens for low SFRs. Especially for dwarf galaxies the SFRs can be underestimated by up to three orders of magnitude. We revise the existing linear L_Halpha-SFR relations using our IGIMF notion. These are likely to lead to a revision of the cosmological star formation histories. We also demonstrate that in the case of the Sculptor dwarf irregular galaxies the IGIMF-formalism implies a linear dependence of the total SFR on the total galaxy gas mass. A constant gas depletion time scale of a few Gyrs results independently of the galaxy gas mass with a reduced scatter compared to the conventional results. Our findings are qualitatively independent of the explicit choice of the IGIMF details and challenges current star formation theory in dwarf galaxies.
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