JKCS041 ($z=1.8$) is one of the most distant galaxy cluster systems known, seen when the Universe was less than 4 billion years old. Recent Sunyaev-Zeldovich (SZ) observations show a temperature decrement that is less than expected based on mass estimates of the system from X-ray, weak gravitational lensing and galaxy richness measurements. In this paper we seek to explain the observables - in particular the low SZ decrement and single SZ peak, the projected offset between the X-ray and SZ peaks of $\approx$220 kpc, the gas mass measurements and the lensing mass estimate. We use the GAMER-2 hydrodynamic code to carry out idealized numerical simulations of cluster mergers and compare resulting synthetic maps with the observational data. The observations are not well reproduced by an isolated cluster, while instead they are when considering cluster mergers viewed a few tenths of a Gyr after first core passage. A range of merger scenarios is consistent with the observations, but parts of parameter space can be ruled out, and generically some kind of merger process is necessary to reproduce the offset between the SZ and X-ray peaks. In particular, a total mass of $\approx$2$\times 10^{14} M_\odot$, mass ratio of $\approx$2:3, gas fraction of $0.05-0.1$ and Navarro, Frenk and White (NFW) mass density profile concentration $c$$\approx$5 for both components are scenarios that are consistent with the observational data.
GASTRO library II: Exploring Chemical Bimodalities in Disk Galaxies with GSE-like Mergers and Massive Star-forming Clumps
Shanghai Jiao Tong University（上海交通大学）；Institut de Ciencies del Cosmos (ICCUB), Universitat de Barcelona (IEEC-UB)（巴塞罗那大学宇宙科学研究所）；Observatoire de Paris, Université PSL, Sorbonne Université, Université Paris Cité, CY Cergy Paris Université, CNRS（巴黎天文台）；Kavli IPMU (WPI), UTIAS, The University of Tokyo（东京大学 Kavli 宇宙物理数学研究所）；University of Lancashire（兰开夏大学）；Observatório Nacional（巴西国家天文台）；University of Chicago（芝加哥大学）
Exploring the statistical properties of double radio relics in the TNG-Cluster and TNG300 simulations
Yonsei University（延世大学）；University of California, Davis（加州大学戴维斯分校）；Yale University（耶鲁大学）；California Institute of Technology（加州理工学院）；Harvard-Smithsonian Center for Astrophysics（哈佛-史密森天体物理中心）
Is this an Early Stage Merger? A Case Study on Molecular Gas and Star Formation Properties of Arp 240
我们提出了新的高分辨率$^{12}$ CO $J$ =1-0，$J$ =2-1，和$^{13}$ CO $J$ =1-0地图的早期合并Arp 240（NGC 5257/8）获得的阿塔卡马大型毫米/亚毫米阵列（ALMA）。文献中的模拟表明，合并刚刚完成了第一次通过;然而，我们发现，与典型的紧密星系对相比，该系统具有较低的全球气体分数，但具有较高的恒星形成效率，这表明该系统可能已经处于高级合并阶段。我们将ALMA数据与来自亚毫米波阵列的$^{12}$ CO $J$ =3-2个观测数据相结合，并在几个不同区域进行RADEX建模。RADEX模拟和局部热平衡（LTE）分析表明，该地区最有可能有一个CO到H $_2$转换因子$α_{\mathrm{CO}}$接近或甚至小于（超）亮红外星系的典型值。使用33 GHz的数据从甚大阵列测量恒星形成率，我们发现，大多数恒星形成区域的分子气体耗尽时间小于1亿年。我们计算了不同区域每自由落体时间的恒星形成效率（SFE），发现有些区域的值似乎大于100%。我们发现这些区域通常显示出年轻大质量星团（YMC）的证据。在探讨了各种因素后，我们认为这主要是由于这些地区的射电连续辐射主要来自YMC，这导致高估了每个自由落体时间的SFE。
Deep Extragalactic VIsible Legacy Survey (DEVILS): Morphologically-selected galaxy merger fractions and their direct comparison to close-pair samples
The University of Western Australia（西澳大利亚大学）；Monash University（莫纳什大学）；Instituto Astrofisica de Canarias（加那利天体物理研究所）；Institute of Space Sciences (ICE, CSIC)（空间科学研究所）
Chemical decoding of kinematic substructures in the Galactic halo
Università 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）；Observatoire de Paris, Université PSL, Sorbonne Université, Université Paris Cité, CY Cergy Paris Université, CNRS（巴黎天文台，巴黎文理研究大学，索邦大学，巴黎西岱大学，CY塞尔吉巴黎大学，法国国家科学研究中心）；CEA, AIM, Université Paris-Saclay（法国原子能和替代能源委员会，天体物理学和粒子物理研究所，巴黎萨克雷大学）；Leibniz Institut für Astrophysik Potsdam (AIP)（波茨坦莱布尼茨天体物理研究所）；Dipartimento di Fisica e Astronomia “Galileo Galilei”, Università di Padova（帕多瓦大学伽利略·伽利莱物理与天文学系）；Dipartimento di Tecnica e Gestione dei Sistemi Industriali, Università di Padova（帕多瓦大学工业系统技术与管理系）；INAF – Osservatorio Astronomico di Padova（意大利国家天体物理研究所帕多瓦天文台）
