The Next Generation Very Large Array (ngVLA) has excellent capabilities to unveil various dynamical and chemical processes in massive star formation at the unexplored innermost regions. Based on the recent observations of ALMA/VLA as well as theoretical predictions, we propose several intriguing topics in massive star formation from the perspective of the ngVLA. In the disk scale of $\lesssim$ 100 au around massive protostars, dust grains are expected to be destructed/sublimated because the physical conditions of temperature, shocks, and radiation are much more intense than those in the envelopes, which are typically observed as hot cores. The high sensitivity and resolution of the ngVLA will enable us to detect the gaseous refractories released by dust destruction, e.g., SiO, NaCl, and AlO, which trace disk kinematics and give new insights into the metallic elements in star-forming regions, i.e., astromineralogy. The multi-epoch survey by the ngVLA will provide demographics of forming massive multiples with separations of $\lesssim$ 10 au with their proper motion. Combining with observations of refractory molecular lines and hydrogen recombination lines, we can reproduce the three-dimensional orbital motions of massive proto-binaries. Moreover, the 1-mas resolution of the ngVLA could possibly take the first-ever picture of the photospheric surface of an accreting protostar, if it is bloated to the au scale by the high accretion rates of mass and thermal energy.
Flyby-induced high-eccentricity migration and the prevalence of hot Jupiters in M67
Institute of Astronomy, University of Cambridge（剑桥大学天文研究所）；Astronomy Unit, Department of Physics and Astronomy, Queen Mary University of London（伦敦大学玛丽女王学院物理与天文学系天体物理组）
The birth of the Milky Way as uncovered by accurate stellar ages with Gaia
了解星系一生中形成的恒星的年龄是了解其形成和演化的基础。然而，恒星年龄很难获得，因为它们无法通过观测来测量，需要与恒星模型（Soderblom 2010）进行比较。另外，年龄分布可以通过颜色-星等图拟合（Gallart et al. 2005）得到，到目前为止主要用于研究附近的星系。从盖亚任务到个别银河系恒星的新距离（Brown et al. 2018）使我们能够使用这种技术从厚盘色星等图和运动学热局部晕的神秘的双序列色星等图中推导出年龄（Babusiaux et al. 2018），其中蓝色序列与重大吸积事件有关（Haywood et al. 2018，Helmi et al. 2018）。由于缺乏准确的年龄，合并的时间及其对银河系早期演化的作用仍然不清楚。我们发现，在这两个晕序列中的恒星具有相同的年龄分布，并且比大部分厚盘星更老。10 Gyr前切割的尖锐晕年龄可以与盖亚-土卫二的吸积相确定。随着星系形成的最先进的宇宙学模拟（布鲁克等人，2012），这些强大的年龄使我们能够对塑造我们银河系的早期事件序列进行排序，确定红色序列是银河系祖先中形成的第一批恒星，由于其运动学，可以被描述为长期寻找的原位晕。
The chemodynamical memory of a major merger in a NIHAO-UHD Milky Way analogue -- II. Were Splash stars heated or already born hot?
Research School of Astronomy and Astrophysics, Australian National University（澳大利亚国立大学天文与天体物理研究学院）；Universität Heidelberg, Interdisziplinäres Zentrum für Wissenschaftliches Rechnen（海德堡大学跨学科科学计算中心）；Universität Heidelberg, Zentrum für Astronomie, Institut für Theoretische Astrophysik（海德堡大学天文学中心理论天体物理研究所）；Dipartimento di Fisica e Astronomia, Universitá degli Studi di Firenze（佛罗伦萨大学物理与天文学系）；The Observatories of the Carnegie Institution for Science（卡内基科学机构天文台）；Institute of Astronomy, University of Cambridge（剑桥大学天文学研究所）；Department of Astronomy, New Mexico State University（新墨西哥州立大学天文学系）
Three-phase Interstellar medium in Galaxies Resolving Evolution with Star formation and Supernova feedback (TIGRESS): Algorithms, Fiducial model, and Convergence
Formation of star clusters and enrichment by massive stars in simulations of low-metallicity galaxies with a fully sampled initial stellar mass function
