Gjöll流和NGC 3201之间的化学动力学联系
A chemo-dynamical link between the Gjöll stream and NGC 3201
摘要：
最近对盖亚第二次数据发布的分析揭示了银河系周围的一些新的恒星流。有人认为其中的一个星流Gjöll与球状星团NGC 3201有关，但到目前为止，这种关联只是基于星流的运动学。在这项工作中，我们确定了盖亚数据中的五个可能的流成员，这些成员足够明亮，可以用麦克唐纳天文台的哈兰·J·史密斯望远镜进行高分辨率光谱跟踪。一颗恒星根据其径向速度被排除在成员之外。对其余四个运动学成员的简要分析显示，其中两颗恒星与NGC 3201有很好的化学匹配，这是由它们相似的Al和$α$元素丰度驱动的。在剩下的两颗中，一颗与NGC 3201没有化学相似性，可能是一颗不相关的银河系晕场星，而另一颗显示出类似的Al丰度，但$α$元素丰度略低。在Gjöll流中的恒星与NGC 3201的化学标记证实了这种关联，并提供了银河系分层形成的直接证据。
英文摘要：
Recent analysis of the second data release of Gaia has revealed a number of new stellar streams surrounding the Milky Way. It has been suggested that one of these streams, Gjöll, is associated with the globular cluster NGC 3201, but thus far the association has only been based on kinematics of the stream stars. In this work we identify five likely stream members in the Gaia data that are bright enough for high-resolution spectroscopic follow-up with the Harlan J. Smith telescope at McDonald Observatory. One star is ruled out as a member based on its radial velocity. Abundance analysis of the remaining four kinematic members reveals a good chemical match to NGC 3201 for two of the stars, driven by their similar Al and $α$-element abundances. Of the remaining two, one shows no chemical similarity to NGC 3201 and is likely an unassociated Milky Way halo field star, while the other exhibits a similar Al abundance but has somewhat lower $α$-element abundances. The chemical tagging of stars in the Gjöll stream to NGC 3201 confirms this association and provides direct proof of the hierarchical formation of the Milky Way.
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