Evidence from the H3 Survey That the Stellar Halo Is Entirely Comprised of Substructure
Evidence from the H3 Survey That the Stellar Halo Is Entirely Comprised of Substructure
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DOI：
10.3847/1538-4357/abaef4
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发表时间：
2020-06
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影响因子：
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通讯作者：
R. Naidu;C. Conroy;A. Bonaca;Benjamin D. Johnson;Y. Ting 丁;N. Caldwell;D. Zaritsky;P. Cargile
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文献类型：
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作者：
R. Naidu;C. Conroy;A. Bonaca;Benjamin D. Johnson;Y. Ting 丁;N. Caldwell;D. Zaritsky;P. Cargile
在ΛCDM范式中，银河系恒星晕被预测为较小系统的吸积碎片的庇护所。为了识别这些系统，H3光谱调查与盖亚相结合，正在收集遥远星系的6D相空间和化学信息。在这里，我们提出了一个全面的库存结构内50千秒差距从银河系中心使用的样本5684巨星在和。我们确定了已知的结构，包括高α盘，原位晕（加热到偏心轨道的盘星），人马座（Sgr），盖亚-香肠-土卫二（GSE），海尔米流，红杉和Thamnos。此外，我们确定了以下新结构：（i）Aleph（[Fe/H] =-0.5），一个低偏心率的结构，令人惊讶地从平面上升了10千秒差距，（ii）和（iii）阿诸那（[Fe/H] =-1.2）和I'itoi（[Fe/H] 80%的晕是由两个大质量（M = 108- 109 M = 108）的吸积矮星构成：GSE（[Fe/H] = −1.2）在25 kpc以内，Sgr（[Fe/H] = −1.0）在25 kpc以上。这就解释了晕的总体金属丰度相对较高（[Fe/H]<$−1.2）。我们将95%的样本归因于其中一个列出的结构，指出一个完全由吸积矮星和加热盘建造的光环。
In the ΛCDM paradigm, the Galactic stellar halo is predicted to harbor the accreted debris of smaller systems. To identify these systems, the H3 Spectroscopic Survey, combined with Gaia, is gathering 6D phase-space and chemical information in the distant Galaxy. Here we present a comprehensive inventory of structure within 50 kpc from the Galactic center using a sample of 5684 giants at and . We identify known structures including the high-α disk, the in situ halo (disk stars heated to eccentric orbits), Sagittarius (Sgr), Gaia–Sausage–Enceladus (GSE), the Helmi Streams, Sequoia, and Thamnos. Additionally, we identify the following new structures: (i) Aleph ([Fe/H] = −0.5), a low-eccentricity structure that rises a surprising 10 kpc off the plane, (ii) and (iii) Arjuna ([Fe/H] = −1.2) and I’itoi ([Fe/H] 80% of the halo is built by two massive (M⋆ ∼ 108–109M⊙) accreted dwarfs: GSE ([Fe/H] = −1.2) within 25 kpc and Sgr ([Fe/H] = −1.0) beyond 25 kpc. This explains the relatively high overall metallicity of the halo ([Fe/H] ≈ −1.2). We attribute ≳95% of the sample to one of the listed structures, pointing to a halo built entirely from accreted dwarfs and heating of the disk.