CHEMICAL SIGNATURE INDICATING A LACK OF MASSIVE STARS IN DWARF GALAXIES
CHEMICAL SIGNATURE INDICATING A LACK OF MASSIVE STARS IN DWARF GALAXIES
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DOI：
10.1088/0004-637x/736/2/113
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发表时间：
2011-05
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影响因子：
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通讯作者：
T. Tsujimoto
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作者：
T. Tsujimoto
越来越多的证据支持附近矮星系中出现的一种不寻常的元素特征，特别是矮椭球体（dSphs），表明星系演化的关键过程与银河系不同。除了众所周知的dSphs中α元素的不足之外，最近的观测清楚地表明，s过程元素（Ba）相对于Fe，α和r过程元素显着增强。这种增强发生在一些dSphs以及大麦哲伦星云中，但在银河系中看不到。在这里，我们报告说，这一特点是缺乏非常大质量的恒星（250万吨）的低星星形成率环境中预测的证据。我们的结论是，矮星系的独特的元素特征，包括在一些低金属丰度的恒星的低α/Fe比，至少在某些部分，其特征在于不同形式的初始质量函数。我们提出了一个详细的天炉座dSph星系的模型，并讨论了其复杂的化学富集的历史与轻s-过程元素Y的核合成网站。
Growing evidence supports an unusual elemental feature appearing in nearby dwarf galaxies, especially dwarf spheroidals (dSphs), indicating a key process of galaxy evolution that is different from that of the Galaxy. In addition to the well-known deficiency of α-elements in dSphs, recent observations have clearly shown that s-process elements (Ba) are significantly enhanced relative to Fe, α-, and r-process elements. This enhancement occurs in some dSphs as well as in the Large Magellanic Cloud, but is unseen in the Galaxy. Here we report that this feature is evidence of the lack of very massive stars (≳25 M☉) as predicted in the low star formation rate environment. We conclude that the unique elemental feature of dwarf galaxies including a low α/Fe ratio in some low-metallicity stars is, at least in some part, characterized by a different form of the initial mass function. We present a detailed model for the Fornax dSph galaxy and discuss its complex chemical enrichment history together with the nucleosynthesis site of the light s-process element Y.