Neutron Star Mergers are the Dominant Source of the r-process in the Early Evolution of Dwarf Galaxies
Neutron Star Mergers are the Dominant Source of the r-process in the Early Evolution of Dwarf Galaxies
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中子星合并是矮星系早期演化中 r 过程的主要来源
DOI：
10.3847/1538-4357/aaeb8e
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发表时间：
2018
期刊：
影响因子：
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通讯作者：
S. Korotin
中科院分区：
文献类型：
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作者：
G. Duggan;E. Kirby;S. Andrievsky;S. Korotin
r过程有许多候选地点：核心坍缩超新星（CCSNe，包括罕见的磁旋核心坍缩超新星）、中子星合并（nsm）和中子星/黑洞合并。星系（特别是矮星系）的化学富集有助于根据r过程元素的持续积累来区分这些来源。这项技术可以通过最明显的观测差异来区分r过程的候选位置——这些事件在恒星形成后发生的速度有多快。附近几个矮星系的存在使我们能够测量具有不同恒星形成历史的星系的强大化学丰度。矮星系特别有用，因为简单的化学演化模型可以用来确定r过程物质的来源。用Keck/DEIMOS中分辨率光谱法对r过程元素钡进行了测量。我们展示了迄今为止在矮星系中收集的最大的钡丰度样本（近250颗恒星）。我们测量了样品中[Ba/Fe]作为[Fe/H]的函数，并与现有的[α/Fe]测量结果进行了比较。我们发现，为了解释我们观察到的丰度，钡的大量贡献需要在更延迟的时间尺度上发生，而不是CCSNe，即与[Mg/Fe]和[Fe/H]趋势相比，[Ba/Fe]和[Fe/H]的r-过程分量明显更积极的趋势。我们得出结论，nsm是矮星系早期r过程富集的最可能来源。
There are many candidate sites of the r-process: core-collapse supernovae (CCSNe; including rare magnetorotational core-collapse supernovae), neutron star mergers (NSMs), and neutron star/black hole mergers. The chemical enrichment of galaxies—specifically dwarf galaxies—helps distinguish between these sources based on the continual build-up of r-process elements. This technique can distinguish between the r-process candidate sites by the clearest observational difference—how quickly these events occur after the stars are created. The existence of several nearby dwarf galaxies allows us to measure robust chemical abundances for galaxies with different star formation histories. Dwarf galaxies are especially useful because simple chemical evolution models can be used to determine the sources of r-process material. We have measured the r-process element barium with Keck/DEIMOS medium-resolution spectroscopy. We present the largest sample of barium abundances (almost 250 stars) in dwarf galaxies ever assembled. We measure [Ba/Fe] as a function of [Fe/H] in this sample and compare with existing [α/Fe] measurements. We have found that a large contribution of barium needs to occur at more delayed timescales than CCSNe in order to explain our observed abundances, namely the significantly more positive trend of the r-process component of [Ba/Fe] versus [Fe/H] seen for when compared to the [Mg/Fe] versus [Fe/H] trend. We conclude that NSMs are the most likely source of r-process enrichment in dwarf galaxies at early times.