Enrichment history of r-process elements in the Galactic halo and dwarf galaxies

快速中子俘获过程（r-过程）产生大多数比铁重的元素。最近的核合成研究指出，超新星作为r-过程位置的候选者存在严重困难。另一个强有力的候选者是中子星星合并。然而，有人认为中子星星合并不能解释在贫金属恒星中观测到的r过程元素的增强，因为合并的时间尺度被认为太长了，达1亿年。在这项研究中，使用一个新的化学演化模型，我们已经表明，中子星星合并可以重现观测丰度的贫金属恒星，如果银河系的晕形成的子晕与各种星星形成历史的集群。这一结果强烈支持中子星星合并的r-过程网站。

Rapid neutron-capture process (r-process) produces most elements heavier than iron. Recent nucleosynthesis studies have pointed out serious difficulties for supernovae as a candidate of the r-process site. The other strong candidate is a neutron star merger. However, it has been suggested that neutron star mergers could not explain observed enhancement of r-process elements in metal-poor stars because the timescale of merger is regarded to be too long as 100 Myrs. In this study, using a new chemical evolution model, we have shown that neutron star mergers could reproduce observational abundances of metal-poor stars if the Galactic halo were formed from clusterings of sub-halos with various star formation histories. This result strongly supports neutron star mergers as the r-process site.