On the Hunt for the Origins of the Orphan–Chenab Stream: Detailed Element Abundances with APOGEE and Gaia
On the Hunt for the Origins of the Orphan–Chenab Stream: Detailed Element Abundances with APOGEE and Gaia
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DOI：
10.3847/1538-4357/acb698
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发表时间：
2022-05
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通讯作者：
K. Hawkins;A. Price-Whelan;Allyson A. Sheffield;Aidan Z. Subrahimovic;R. Beaton;V. Belokurov;D. Erkal;Sergey E. Koposov;R. Lane;C. Laporte;C. Nitschelm
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作者：
K. Hawkins;A. Price-Whelan;Allyson A. Sheffield;Aidan Z. Subrahimovic;R. Beaton;V. Belokurov;D. Erkal;Sergey E. Koposov;R. Lane;C. Laporte;C. Nitschelm
银河晕中的恒星流是银河系等星系集合的有用探测器。近年来发现的许多潮汐星流都伴随着一个已知的球状星系团或矮星系。然而，孤儿-切纳布(OC)流是一个例子，在那里发现了一个相对较窄的恒星流，但没有已知的祖先。为了找到OC流的母体，我们使用了欧空局GAIA任务(GAIA EDR3)早期第三次数据发布的天体测量和斯隆数字天空调查(SDSS)-IV阿帕奇点天文台星系演化实验(APOEE)调查的径向速度信息，以找到多达13颗可能是OC流成员的恒星。我们利用远地点观测研究了α(O、Mg、Ca、Si、Ti和S)、奇数Z(Al、K和V)、Fe峰(Fe、Ni、Mn、Co和Cr)和中子俘获(Ce)元素群中OC流的化学性质(最多10颗星)。我们发现组成OC流的恒星与单金属群不一致，金属丰度的中位数为−1.92Dex，色散为0.28Dex。我们的结果还表明，与已知的银河系种群相比，α元素是贫化的，其[Mg/Al]丰度比与球状星团的第二代恒星不一致。这些恒星的详细化学模式，即[α/Fe]-[Fe/H]平面和金属丰度分布表明，OC流前体很可能是一个质量为∼106M⊙的矮球星系。
Stellar streams in the Galactic halo are useful probes of the assembly of galaxies like the Milky Way. Many tidal stellar streams that have been found in recent years are accompanied by a known progenitor globular cluster or dwarf galaxy. However, the Orphan–Chenab (OC) stream is one case where a relatively narrow stream of stars has been found without a known progenitor. In an effort to find the parent of the OC stream, we use astrometry from the early third data release of ESA’s Gaia mission (Gaia EDR3) and radial velocity information from the Sloan Digital Sky Survey (SDSS)-IV Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey to find up to 13 stars that are likely members of the OC stream. We use the APOGEE survey to study the chemical nature (for up to 10 stars) of the OC stream in the α (O, Mg, Ca, Si, Ti, and S), odd-Z (Al, K, and V), Fe-peak (Fe, Ni, Mn, Co, and Cr), and neutron-capture (Ce) elemental groups. We find that the stars that make up the OC stream are not consistent with a monometallic population and have a median metallicity of −1.92 dex with a dispersion of 0.28 dex. Our results also indicate that the α elements are depleted compared to the known Milky Way populations and that its [Mg/Al] abundance ratio is not consistent with second-generation stars from globular clusters. The detailed chemical pattern of these stars, namely the [α/Fe]–[Fe/H] plane and the metallicity distribution, indicates that the OC stream progenitor is very likely to be a dwarf spheroidal galaxy with a mass of ∼106 M ⊙.