Broken into Pieces: ATLAS and Aliqa Uma as One Single Stream
Broken into Pieces: ATLAS and Aliqa Uma as One Single Stream
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DOI：
10.3847/1538-4357/abeb18
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发表时间：
2020-06
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通讯作者：
Ting S. Li;Sergey E. Koposov;D. Erkal;A. Ji;N. Shipp;A. Pace;T. Hilmi;K. Kuehn;G. Lewis
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作者：
Ting S. Li;Sergey E. Koposov;D. Erkal;A. Ji;N. Shipp;A. Pace;T. Hilmi;K. Kuehn;G. Lewis
我们提出了第一次光谱测量的ATLAS和Aliqa乌玛流从南方恒星流光谱调查（S 5），结合光度数据从暗能量调查和天体测量数据从盖亚。从径向速度和自行的光谱成员的相干性，我们发现，这两个系统极有可能是一个流的不连续的形态和密度的天空（“扭结”的功能）。我们将这整个流称为ATLAS-Aliqa Uma流，或AAU流。我们进行了一个全面的重子子结构的效果的探索，发现只有遇到人马座矮20.5 Gyr前可以创建一个功能类似于观察到的“扭结”。此外，我们还确定了ATLAS组件中的两个缺口与流宽度的扩大（“扩大”功能）。这些间隙可能是由小质量扰动造成的，例如暗物质晕，因为AAU流是已知的最遥远的冷流，流表面密度和天空中的流轨迹都有严重变化。利用流迹、流距和运动学信息，我们确定了AAU流的轨道，发现它受到大麦哲伦云的影响，导致自行与流迹不重合。与Orphan-Chenab流一起，AAU是第二个被发现是由外部扰动分成两段的单一流对。
We present the first spectroscopic measurements of the ATLAS and Aliqa Uma streams from the Southern Stellar Stream Spectroscopic Survey (S 5), in combination with the photometric data from the Dark Energy Survey and astrometric data from Gaia. From the coherence of spectroscopic members in radial velocity and proper motion, we find that these two systems are extremely likely to be one stream with discontinuity in morphology and density on the sky (the “kink” feature). We refer to this entire stream as the ATLAS-Aliqa Uma stream, or the AAU stream. We perform a comprehensive exploration of the effect of baryonic substructures and find that only an encounter with the Sagittarius dwarf ∼0.5 Gyr ago can create a feature similar to the observed “kink.” In addition, we also identify two gaps in the ATLAS component associated with the broadening in the stream width (the “broadening” feature). These gaps have likely been created by small mass perturbers, such as dark matter halos, as the AAU stream is the most distant cold stream known with severe variations in both the stream surface density and the stream track on the sky. With the stream track, stream distance, and kinematic information, we determine the orbit of the AAU stream and find that it has been affected by the Large Magellanic Cloud, resulting in a misalignment between the proper motion and stream track. Together with the Orphan-Chenab Stream, AAU is the second stream pair that has been found to be a single stream separated into two segments by external perturbation.