Kinematic data rebuild the nuclear star cluster as the most metal-rich region of the Galaxy
Kinematic data rebuild the nuclear star cluster as the most metal-rich region of the Galaxy
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运动数据将核星团重建为银河系金属最丰富的区域
DOI：
10.1051/0004-6361/202244411
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
F. Nogueras
中科院分区：
文献类型：
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作者：
F. Nogueras
银河系中心（GC）距离地球仅8千秒差距，是了解银河系核心的独特模板。然而，GC的高度拥挤和消光阻碍了对其主要恒星组成部分--核星盘（NSD）和核星星团（NSC）的研究。最近的工作表明，NSD和NSC可以通过它们的恒星的不同消光来区分沿着朝向NSC的视线。这促使我们分析自行，径向速度，和不同的灭绝群体的金属丰度分布。我们使用光度，运动学和金属丰度数据来区分可能的NSD和NSC恒星在一个地区的NSC为中心。我们发现了两个不同的灭绝恒星群，并获得了显着不同的自行分布，为他们每个人，在NSD和NSC的预期运动学一致。我们得出的径向速度图，似乎是不同的NSD和NSC。我们还发现每个组成部分的金属丰度不同，其中最大的一个是在最熄灭的恒星群中测量的。我们得到，每个消光组的金属丰度分布是最好的双峰分布拟合，表明存在两个金属丰度分量为每个（一个广泛的略低于太阳金属丰度，和一个更丰富的金属窄，这是最大的高消光组的恒星）。我们的结论是，这两个灭绝组是不同的GC组件具有不同的运动学和金属丰度，并对应于NSD和NSC。因此，可以通过它们的不同灭绝来区分它们。NSC富金属星的高平均金属丰度$[M/H]\sim0.3 $\，dex支持了NSC可能是银河系中最富金属的区域。
The Galactic centre (GC) is located at only 8 kpc from Earth and constitutes a unique template to understand Galactic nuclei. Nevertheless, the high crowding and extinction towards the GC hamper the study of its main stellar components, the nuclear stellar disc (NSD) and the nuclear star cluster (NSC). Recent work has suggested that the NSD and the NSC can be distinguished along the line of sight towards the NSC via the different extinction of their stars. This motivated us to analyse the proper motion, radial velocity, and the metallicity distributions of the different extinction groups. We use photometric, kinematic, and metallicity data to distinguish between probable NSD and NSC stars in a region centred on the NSC. We detected two different extinction groups of stars and obtained significantly different proper motion distributions for each of them, in agreement with the expected kinematics for the NSD and the NSC. We derived radial velocity maps that appear to be different for the NSD and the NSC. We also found different metallicities for each of the components, with the largest one measured for the most extinguished group of stars. We obtained that the metallicity distribution of each extinction group is best fitted by a bimodal distribution, indicating the presence of two metallicity components for each of them (a broad one slightly below solar metallicity, and a more metal rich narrower one, that is largest for the high extinction group of stars). We conclude that both extinction groups are distinct GC components with different kinematics and metallicity, and correspond to the NSD and the NSC. Therefore, it is possible to distinguish them via their different extinction. The high mean metallicity, $[M/H]\sim0.3$\,dex, obtained for the NSC metal rich stars, supports that the NSC is arguabily the most metal rich region of the Galaxy.