Chemical evolution models for the dwarf spheroidal galaxies Leo 1 and Leo 2
Chemical evolution models for the dwarf spheroidal galaxies Leo 1 and Leo 2
复制标题
矮椭球星系 Leo 1 和 Leo 2 的化学演化模型
DOI：
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发表时间：
2010
期刊：
影响因子：
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通讯作者：
F. Matteucci
中科院分区：
文献类型：
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作者：
G. Lanfranchi;F. Matteucci
目标。通过详细的化学演化模型与观测结果的比较，我们研究了矮小球状星系LEO1和LEO2的化学演化历史。该模型采用了最新的核合成，并考虑了不同类型超新星(Ia，II)的作用，使我们能够详细跟踪几种化学元素(H，D，He，C，N，O，Mg，Si，S，Ca，Fe，Ba和Eu)的演化。方法：研究方法。每个星系模型都由恒星形成率和银河系风效率的规定来确定，以再现这些星系的主要特征，特别是恒星的金属丰度分布和几个丰度比。这些参数受观测到的颜色-星等图所推断的星系恒星形成历史的限制，这表明恒星形成时间较长，发生在早期，但也有中间恒星群的迹象。结果。LEO1和LEO2星系的主要观测特征可以用化学演化模型很好地解释，根据以下情景：恒星形成在14Gyr和9Gyr前的两个长事件中，分别持续了5Gyr和7Gyr，效率较低(ν=0。6Gyr−1)，而LEO2的恒星形成历史以14Gyr前的一次事件为特征，持续7Gyr，效率也很低(ν=0)。3G年−1)。在这两个星系中都出现了强风(分别是恒星形成速率的9倍和8倍，在LEO1和LEO2中，wi分别为9和8)，这决定了中等到高金属丰度比的模式和恒星金属丰度分布的形状。结论。只有在假设气体被星系风吹走的情况下，观测约束才能重现。
Aims. We investigate the chemical evolutionary history of the dwarf spheroidal galaxies Leo 1 and Leo 2 by means of predictions from a detailed chemical evolution model compared to observations. The model adopts up to date nucleosynthesis and takes into account the role played by supernovae of different types (Ia, II), allowing us to follow in detail the evolution of several chemical elements (H, D, He, C, N, O, Mg, Si, S, Ca, Fe, Ba, and Eu). Methods. Each galaxy model is specified by the prescriptions of the star formation rate and by the galactic wind efficiency chosen to reproduce the main features of these galaxies, in particular the stellar metallicity distributions and several abundance ratios. These parameters are constrained by the star formation histories of the galaxies as inferred by the observed color–magnitude diagrams, indicating extended star formation episodes occurring at early epochs, but also with hints of intermediate stellar populations. Results. The main observed features of the galaxies Leo 1 and Leo 2 can be very well explained by chemical evolution models according to the following scenarios: the star formation occurred in two long episodes at 14 Gyr and 9 Gyr ago that lasted 5 and 7 Gyr, respectively, with a low efficiency (ν = 0. 6G yr −1 ) in Leo 1, whereas the star formation history in Leo 2 is characterized by one episode at 14 Gyr ago that lasted 7 Gyr, also with a low efficiency (ν = 0. 3G yr −1 ). In both galaxies an intense wind (nine and eight times the star formation rate – wi = 9 and 8 in Leo 1 and Leo 2, respectively) takes place which defines the pattern of the abundance ratios and the shape of the stellar metallicity distribution at intermediate to high metallicities. Conclusions. The observational constraints can only be reproduced with the assumption of gas removal by galactic winds.