Milky Way's Eccentric Constituents with Gaia, APOGEE, and GALAH
Milky Way's Eccentric Constituents with Gaia, APOGEE, and GALAH
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DOI：
10.3847/1538-4357/ac8d68
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发表时间：
2022-06
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通讯作者：
G. Myeong;V. Belokurov;D. Aguado;N. Evans;N. Caldwell;James Bradley Harvard-Smithsonian Center for Astrophysics-James-Bradley-Harvard-Smithsonian-Center-for-2264712550;I. O. Astronomy;Cambridge University;Center for Computational Astrophysics;Flatiron Institute;Dipartimento di Fisica e Astrofisica;I. Arcetri
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作者：
G. Myeong;V. Belokurov;D. Aguado;N. Evans;N. Caldwell;James Bradley Harvard-Smithsonian Center for Astrophysics-James-Bradley-Harvard-Smithsonian-Center-for-2264712550;I. O. Astronomy;Cambridge University;Center for Computational Astrophysics;Flatiron Institute;Dipartimento di Fisica e Astrofisica;I. Arcetri
我们报道了化学动力学空间中局部恒星晕的无监督分解的结果，该结果由远地点DR17和GALAH DR3的丰度测量所跨越。在我们的高斯混合模型中，只有四个独立的分量主导着太阳近邻的晕，三个以前已知的分量，极光，飞溅，和盖亚香肠/土卫二(GS/E)，以及一个新的，Eos。在这四个星系中，只有一个是原生的，即GS/E，这支持了早先的说法，即GS/E是银河系恒星晕的主要起源。我们表明，极光与所谓的赫拉克勒斯合并的化学性质完全一致。在我们的分析中，没有应用预定义的化学选择切割，极光覆盖了大范围的[Al/Fe]，金属丰度关联表明，在年轻的银河系这个大质量星系中，化学物质快速浓缩。被称为Eos的新晕组分因其高平均值[Al/Fe]而被归类为原地晕。EOS表现出强烈的演化作为[Fe/H]的函数，它从最低时最接近GS/E的[Fe/H]变化到与最高时的低α群体[Fe/H]难以区分。我们推测，银河系至少有一部分外薄盘是在受到GS/E污染的气体中开始演化的，而Eos就是这一过程的证据。
We report the results of an unsupervised decomposition of the local stellar halo in the chemodynamical space spanned by the abundance measurements from APOGEE DR17 and GALAH DR3. In our Gaussian mixture model, only four independent components dominate the halo in the solar neighborhood, three previously known, Aurora, Splash, and Gaia-Sausage/Enceladus (GS/E), and one new, Eos. Only one of these four is of accreted origin, namely, the GS/E, thus supporting the earlier claims that the GS/E is the main progenitor of the Galactic stellar halo. We show that Aurora is entirely consistent with the chemical properties of the so-called Heracles merger. In our analysis in which no predefined chemical selection cuts are applied, Aurora spans a wide range of [Al/Fe] with a metallicity correlation indicative of a fast chemical enrichment in a massive galaxy, the young Milky Way. The new halo component dubbed Eos is classified as in situ given its high mean [Al/Fe]. Eos shows strong evolution as a function of [Fe/H], where it changes from being the closest to GS/E at its lowest [Fe/H] to being indistinguishable from the Galactic low-α population at its highest [Fe/H]. We surmise that at least some of the outer thin disk of the Galaxy started its evolution in the gas polluted by the GS/E, and Eos is evidence of this process.