Timing the Early Assembly of the Milky Way with the H3 Survey
Ana Bonaca, Charlie Conroy, Phillip A. Cargile, Rohan P. Naidu, Benjamin D. Johnson, Dennis Zaritsky, Yuan-Sen Ting, Nelson Caldwell, Jiwon Jesse Han, Pieter van Dokkum
The archaeological record of stars in the Milky Way opens a uniquely detailed window into the early formation and assembly of galaxies. Here we use 11,000 main-sequence turn-off stars with well-measured ages, [Fe/H], [$α$/Fe], and orbits from the H3 Survey and Gaia to time the major events in the early Galaxy. Located beyond the Galactic plane, $1\lesssim |Z|/\rm kpc \lesssim4$, this sample contains three chemically distinct groups: a low metallicity population, and low-$α$ and high-$α$ groups at higher metallicity. The age and orbit distributions of these populations show that: 1) the high-$α$ group, which includes both disk stars and the in-situ halo, has a star-formation history independent of eccentricity that abruptly truncated $8.3\pm0.1$ Gyr ago ($z\simeq1$); 2) the low metallicity population, which we identify as the accreted stellar halo, is on eccentric orbits and its star formation truncated $10.2.^{+0.2}_{-0.1}$ Gyr ago ($z\simeq2$); 3) the low-$α$ population is primarily on low eccentricity orbits and the bulk of its stars formed less than 8 Gyr ago. These results suggest a scenario in which the Milky Way accreted a satellite galaxy at $z\approx2$ that merged with the early disk by $z\approx1$. This merger truncated star formation in the early high-$α$ disk and perturbed a fraction of that disk onto halo-like orbits. The merger enabled the formation of a chemically distinct, low-$α$ disk at $z\lesssim1$. The lack of any stars on halo-like orbits at younger ages indicates that this event was the last significant disturbance to the Milky Way disk.
Mass Assembly and Chemical Complexity in the Milky Way
UK Astronomy Technology Centre（英国天文技术中心）；University of Bath（巴斯大学）；INAF-IAPS（意大利国家天体物理研究所-行星科学研究所）；Max Planck Institute for Astronomy（马克斯·普朗克天文学研究所）；INAF–Osservatorio Astrofisico di Arcetri（意大利国家天体物理研究所-阿切特里天文台）；Observatoire Astronomique de Strasbourg（斯特拉斯堡天文台）；University of Hertfordshire（赫特福德大学）；Centro de Astrobiología, CSIC–INTA（西班牙国家航空航天技术研究院-西班牙国家科学研究委员会天体生物学中心）；Max Planck Institute for Radio Astronomy（马克斯·普朗克射电天文研究所）；NRC Herzberg Astronomy & Astrophysics（加拿大国家研究委员会赫茨伯格天文学与天体物理学研究所）；Niels Bohr Institute, University of Copenhagen（哥本哈根大学尼尔斯·玻尔研究所）；Academia Sinica Institute of Astronomy & Astrophysics（中央研究院天文及天文物理研究所）；European Southern Observatory（欧洲南方天文台）；Max Planck Institute for Extraterrestrial Physics（马克斯·普朗克地外物理研究所）
Cluster Ages to Reconstruct the Milky Way Assembly (CARMA). V. The chronological merger tree of the Milky Way
Universidade de Vigo（维戈大学）；Universidad de La Laguna（拉古纳大学）；INAF - Osservatorio di Astrofisica e Scienza dello Spazio di Bologna（意大利国家天体物理研究所博洛尼亚天文与空间科学观测站）；Università degli Studi di Bologna（博洛尼亚大学）；INAF – Osservatorio Astronomico di Abruzzo（意大利国家天体物理研究所阿布鲁佐天文台）；INFN - Sezione di Pisa, Universitá di Pisa（意大利国家核物理研究所比萨分部，比萨大学）；Instituto de Astrofísica de Canarias（加那利天体物理学研究所）
Early steps in the hierarchical assembly of a Milky Way-mass galaxy 1 Gyr after the Big Bang
Dunlap Institute for Astronomy and Astrophysics（邓拉普天体物理与天文研究所）；Department of Astronomy and Physics and Institute for Computational Astrophysics, Saint Mary’s University（圣玛丽大学天文物理系及计算天体物理研究所）；Waseda Research Institute for Science and Engineering, Faculty of Science and Engineering, Waseda University（早稻田大学理工学部理工学研究科）；Kapteyn Astronomical Institute, University of Groningen（格罗宁根大学卡佩恩天文研究所）；Faculty of Mathematics and Physics, University of Ljubljana（卢布尔雅那大学数学物理学院）；Department of Physics and Astronomy, University of California Davis（加州大学戴维斯分校物理与天文学系）
Cluster Ages to Reconstruct the Milky Way Assembly (CARMA). II. The age-metallicity relation of Gaia-Sausage-Enceladus globular clusters
Universidade de Vigo（维戈大学）；Universidad de La Laguna（拉古纳大学）；INAF - Osservatorio di Astrofisica e Scienza dello Spazio di Bologna（博洛尼亚天文物理与空间科学研究所）；INAF – Osservatorio Astronomico di Roma（罗马天文台）；INAF – Osservatorio Astronomico di Abruzzo（阿布鲁佐天文台）；INFN - Sezione di Pisa, Universitá di Pisa（比萨大学及意大利国家核物理研究所比萨分部）；Instituto de Astrofísica de Canarias（加那利群岛天体物理学研究所）；Dipartimento di Fisica e Astronomia, Università degli Studi di Bologna（博洛尼亚大学物理与天文学系）；Universidad de Granada（格拉纳达大学）
Constraints on the assembly history of the Milky Way's smooth, diffuse stellar halo from the metallicity-dependent, radially-dominated velocity anisotropy profiles probed with K giants and BHB stars using LAMOST, SDSS/SEGUE, and Gaia
NEFERTITI: Linking early galaxy formation to the assembly of the Milky Way
INAF/Osservatorio Astrofisico di Arcetri（意大利国家天体物理研究所阿切特里天文台）；Cosmic Dawn Center (DAWN)（宇宙黎明中心）；Niels Bohr Institute, University of Copenhagen（哥本哈根大学尼尔斯玻尔研究所）；Instituto de Astrofísica de Canarias（加那利群岛天体物理研究所）；Universidad de La Laguna（拉古纳大学）
The E-MOSAICS project: tracing galaxy formation and assembly with the age-metallicity distribution of globular clusters
我们提出了25个宇宙学放大模拟银河系质量的星系在“建模星团人口大会在宇宙学模拟内鹰”（E-MOSAICS）项目。E-MOSAICS将星团形成、演化和分裂的详细物理模型与EAGLE星系形成模拟相结合。这使得以下的共同形成和共同进化的星系和他们的星团人口，从而实现了长期的承诺，使用球状星团（GC）作为示踪剂的星系形成和组装。模拟结果表明，年龄金属丰度分布的GC人口表现出强烈的星系到星系的变化，导致其演化历史的差异。我们开发了一种形式主义，系统地限制使用GC年龄金属丰度分布星系的组装历史。这些分布的特点是通过13个指标，我们相关的30个数量描述星系形成和组装（如晕属性，形成/组装红移，恒星质量组装时间尺度，星系合并统计），导致20个统计（高度）显着的相关性。GC年龄-金属丰度分布是研究主星系质量增长、金属富集和次合并历史的灵敏探针。没有这样的关系被发现之间的GC和主要的合并，发挥了次主导作用的银河系质量的星系GC的形成。最后，我们展示了GC年龄金属丰度分布如何使宿主星系的合并树的重建，使我们能够确定所有的祖先与质量$M_*\gtrsim10^8$ M $_\odot$的红移$1\leq z\leq2.5$。这些结果表明，宇宙学模拟的共同形成和共同演化的GC和他们的宿主星系成功地解锁的潜力GC作为定量示踪剂的星系形成和组装。
Solving Milky Way-sized Systems with Haskap Pie: A Halo finding Algorithm with efficient Sampling, K-means clustering, tree-Assembly, Particle tracking, Python modules, Inter-code applicability, and Energy solving
University of Illinois at Urbana-Champaign（伊利诺伊大学厄巴纳-香槟分校）；National Center for Supercomputing Applications（超级计算应用国家中心）
The Pristine Inner Galaxy Survey (PIGS) V: a chemo-dynamical investigation of the early assembly of the Milky Way with the most metal-poor stars in the bulge
University of Pennsylvania（宾夕法尼亚大学）；Lund University（隆德大学）；Carleton College（卡尔顿学院）；The University of Texas at Austin（德克萨斯大学奥斯汀分校）；City University of New York（纽约市立大学）
TOPoS VII. Age-metallicity relation in the Galactic halo and assembly of the Milky Way
Univ Rennes, CNRS, IPR (Institut de Physique de Rennes) - UMR 6251（雷恩大学）；Dipartimento di Fisica e Astronomia, Università degli Studi di Firenze（佛罗伦萨大学）；INAF/Osservatorio Astrofisico di Arcetri（意大利国家天体物理研究所阿切特里天文台）；Department of Physics and Astronomy, University of Bologna（博洛尼亚大学）；INAF, Astrophysics and Space Science Observatory（意大利国家天体物理研究所天体物理学与空间科学观测站）；Universidad Andres Bello, Facultad de Ciencias Exactas, Departamento de Física y Astronomía – Instituto de Astrofísica（安德烈斯贝略大学）；LIRA, Observatoire de Paris, Université PSL, Sorbonne Université, Université Paris Cité, CY Cergy Paris Université, CNRS（巴黎天文台）；UPJV, Université de Picardie Jules Verne（亚眠大学）
