INVESTIGATION OF THE PUZZLING ABUNDANCE PATTERN IN THE STARS OF THE FORNAX DWARF SPHEROIDAL GALAXY
INVESTIGATION OF THE PUZZLING ABUNDANCE PATTERN IN THE STARS OF THE FORNAX DWARF SPHEROIDAL GALAXY
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DOI：
10.1088/0004-637x/775/1/12
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发表时间：
2013-08
期刊：
影响因子：
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通讯作者：
Hong-jie Li;W. Cui;Bo Zhang
中科院分区：
文献类型：
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作者：
Hong-jie Li;W. Cui;Bo Zhang
许多研究发现了附近矮星系元素丰度的异常特征。这意味着星系演化的关键因素不同于银河系（MW）。天炉座矮球状星系（天炉座dSph）中恒星的化学丰度提供了很好的信息，为银河系化学演化模型的设置约束。在这项工作中，采用五分量方法，我们拟合了天炉座dSph恒星的丰度，包括α元素，铁族元素和中子捕获元素。对于大多数样本星，各种过程对元素丰度的相对贡献通常不按MW比例。我们发现，大质量恒星对初级α元素和铁族元素的贡献随[Fe/H]的增加而单调增加。这意味着星系风的影响不足以阻止星星的形成，大质量恒星对α元素的贡献并没有在[Fe/H] −0.5时停止。dSph星和MW星之间的各种过程的平均贡献率单调下降的祖星质量的增加。与MW相比，这是天炉座dSph底部重的初始质量函数（IMF）的重要证据。考虑到dSph的底重IMF，可以解释dSph星的[α/Fe]与[Fe/H]、[铁基/Fe]与[Fe/H]以及[中子俘获/Fe]与[Fe/H]的关系。
Many works have found unusual characteristics of elemental abundances in nearby dwarf galaxies. This implies that there is a key factor of galactic evolution that is different from that of the Milky Way (MW). The chemical abundances of the stars in the Fornax dwarf spheroidal galaxy (Fornax dSph) provide excellent information for setting constraints on the models of galactic chemical evolution. In this work, adopting the five-component approach, we fit the abundances of the Fornax dSph stars, including α elements, iron group elements, and neutron-capture elements. For most sample stars, the relative contributions from the various processes to the elemental abundances are not usually in the MW proportions. We find that the contributions from massive stars to the primary α elements and iron group elements increase monotonically with increasing [Fe/H]. This means that the effect of the galactic wind is not strong enough to halt star formation and the contributions from the massive stars to α elements did not halt for [Fe/H] ≲ −0.5. The average contribution ratios of various processes between the dSph stars and the MW stars monotonically decrease with increasing progenitor mass. This is important evidence of a bottom-heavy initial mass function (IMF) for the Fornax dSph, compared to the MW. Considering a bottom-heavy IMF for the dSph, the observed relations of [α/Fe] versus [Fe/H], [iron group/Fe] versus [Fe/H], and [neutron-capture/Fe] versus [Fe/H] for the dSph stars can be explained.