武仙座矮球状星系的异常化学成分
The Highly Unusual Chemical Composition of the Hercules Dwarf Spheroidal Galaxy
摘要：
本文报道了武仙座矮球状星系中两颗红巨星的丰度分析结果。这些恒星在中子捕获元素中表现出显着的不足，而流体静力学α元素（O，Mg）则强烈增强。我们的数据表明[Ba/Fe]和[Mg/Fe]丰度比分别<-2 dex和~+0.8 dex，基本上没有检测到其他n-捕获元素。与另一颗具有类似丰度模式的dSph星Dra 119相比，它的金属丰度非常低，[Fe/H]=-2.95 dex，而我们的天体[Fe/H]~-2.0 dex，只是中等程度的贫金属。测量的流体静力/爆炸α元素的比例表明，高质量（~35 M_sun）II型超新星的祖先是主要的，如果不是唯一的，这个星系的富集的贡献者。这表明，恒星的形成和化学富集在超微弱的dSphs进行随机和不均匀的小尺度上，或者说，IMF强烈倾斜的高质量恒星。我们恒星的中子俘获缺陷和[Co/Fe]和[Cr/Fe]丰度比与极低金属丰度的星系晕相似。这表明，要么我们的恒星主要由第一个大质量的第III族恒星的喷出物组成（但在适度高的[Fe/H]），要么武仙座星系中的SN喷出物被稀释了约30倍的氢，而不是典型的极端贫金属恒星。
英文摘要：
We report on the abundance analysis of two red giants in the faint Hercules dwarf spheroidal (dSph) galaxy. These stars show a remarkable deficiency in the neutron-capture elements, while the hydrostatic alpha-elements (O, Mg) are strongly enhanced. Our data indicate [Ba/Fe] and [Mg/Fe] abundance ratios of <-2 dex and ~+0.8 dex, respectively, with essentially no detection of other n-capture elements. In contrast to the only other dSph star with similar abundance patterns, Dra 119, which has a very low metallicity at [Fe/H]=-2.95 dex, our objects, at [Fe/H]~-2.0 dex, are only moderately metal poor. The measured ratio of hydrostatic/explosive alpha-elements indicates that high-mass (~35 M_sun) Type II supernovae progenitors are the main, if not only, contributors to the enrichment of this galaxy. This suggests that star formation and chemical enrichment in the ultrafaint dSphs proceeds stochastically and inhomogeneously on small scales, or that the IMF was strongly skewed to high mass stars. The neutron capture deficiencies and the [Co/Fe] and [Cr/Fe] abundance ratios in our stars are similar to those in the extremely low metallicity Galactic halo. This suggests that either our stars are composed mainly of the ejecta from the first, massive, population III stars (but at moderately high [Fe/H]), or that SN ejecta in the Hercules galaxy were diluted with ~30 times less hydrogen than typical for extreme metal-poor stars.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
