DESI Observations of the Andromeda Galaxy: Revealing the Immigration History of Our Nearest Neighbor
DESI Observations of the Andromeda Galaxy: Revealing the Immigration History of Our Nearest Neighbor
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仙女座星系的DESI观测：揭示我们最近邻居的移民历史
DOI：
10.3847/1538-4357/aca5f8
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发表时间：
2022-08
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通讯作者：
A. Dey;J. Najita;Sergey E. Koposov;J. Josephy-Zack;Gabriel Maxemin;E. Bell;C. Poppett;E. Patel;L. Silva;A. Raichoor;D. Schlegel;D. Lang;A. Meisner;A. Myers;J. Aguilar;S. Ahlen;C. Prieto;D. Brooks;A. Cooper;K. Dawson;A. Macorra;P. Doel;A. Font-Ribera;J. García-Bellido;S. Gontcho;J. Guy;K. Honscheid;R. Kehoe;T. Kisner;A. Kremin;M. Landriau;L. Guillou;M. Levi;T. Li;P. Martini;R. Miquel;J. Moustakas;J. Nie;N. Palanque-Delabrouille;F. Prada;E. Schlafly;R. Sharples;G. Tarlé;Y. Ting;L. Tyas;M. Valluri;R. Wechsler;H. Zou
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作者：
A. Dey;J. Najita;Sergey E. Koposov;J. Josephy-Zack;Gabriel Maxemin;E. Bell;C. Poppett;E. Patel;L. Silva;A. Raichoor;D. Schlegel;D. Lang;A. Meisner;A. Myers;J. Aguilar;S. Ahlen;C. Prieto;D. Brooks;A. Cooper;K. Dawson;A. Macorra;P. Doel;A. Font-Ribera;J. García-Bellido;S. Gontcho;J. Guy;K. Honscheid;R. Kehoe;T. Kisner;A. Kremin;M. Landriau;L. Guillou;M. Levi;T. Li;P. Martini;R. Miquel;J. Moustakas;J. Nie;N. Palanque-Delabrouille;F. Prada;E. Schlafly;R. Sharples;G. Tarlé;Y. Ting;L. Tyas;M. Valluri;R. Wechsler;H. Zou
我们展示了暗能量光谱仪器（DESI）对M31内部光晕的观测，它揭示了最近合并的运动学-一个星系移民事件-非常详细。在3.75小时的空中曝光时间内，研究了11,416个源，其中7438个是具有良好测量径向速度的M31源。观测结果揭示了单个恒星的位置和速度中复杂的连贯运动结构：流、楔和v形。虽然之前已经在M31中发现了相干结构的迹象，但这是第一次在银河系以外的星系中看到如此详细和清晰的结构。我们在巨大恒星流、东北陆架和西部陆架地区发现了壳结构的明确运动学证据。运动学与动力学模型的预测非常相似，动力学模型是用来解释内晕的空间形态的。该结果与M31内晕的大部分亚结构是由1-2 Gyr前的一次星系迁移事件产生的解释一致。在所有探测到的亚结构中都存在大量富金属恒星（[Fe/H] >−0.5），这表明移民星系具有较长的恒星形成历史。我们还研究了壳层和巨恒星流对M31引力势的约束能力，并估计在125kpc的投影半径内的质量为log10MNFW(<125kpc)/M⊙=11.80−0.10+0.12。这些结果预示着我们在银河系尺度上研究恒星和星系迁移历史的能力进入了一个新时代。
We present Dark Energy Spectroscopic Instrument (DESI) observations of the inner halo of M31, which reveal the kinematics of a recent merger—a galactic immigration event—in exquisite detail. Of the 11,416 sources studied in 3.75 hr of on-sky exposure time, 7438 are M31 sources with well-measured radial velocities. The observations reveal intricate coherent kinematic structure in the positions and velocities of individual stars: streams, wedges, and chevrons. While hints of coherent structures have been previously detected in M31, this is the first time they have been seen with such detail and clarity in a galaxy beyond the Milky Way. We find clear kinematic evidence for shell structures in the Giant Stellar Stream, the Northeast Shelf, and Western Shelf regions. The kinematics are remarkably similar to the predictions of dynamical models constructed to explain the spatial morphology of the inner halo. The results are consistent with the interpretation that much of the substructure in the inner halo of M31 is produced by a single galactic immigration event 1–2 Gyr ago. Significant numbers of metal-rich stars ([Fe/H] > − 0.5) are present in all of the detected substructures, suggesting that the immigrating galaxy had an extended star formation history. We also investigate the ability of the shells and Giant Stellar Stream to constrain the gravitational potential of M31, and estimate the mass within a projected radius of 125 kpc to be log10MNFW(<125kpc)/M⊙=11.80−0.10+0.12 . The results herald a new era in our ability to study stars on a galactic scale and the immigration histories of galaxies.