用星团年龄重建银河系并合（CARMA）。V.银河系的时间并合树
Cluster Ages to Reconstruct the Milky Way Assembly (CARMA). V. The chronological merger tree of the Milky Way
AI总结：
本研究基于CARMA项目，利用哈勃数据和CARMA代码测定24个球状星团年龄，构建银河系首个严格均匀时间信息的详细并合树，明确各并合事件顺序及贡献质量。
AI中文摘要：
作为“用星团年龄重建银河系并合（CARMA）”项目追踪银河系形成历史工作的一部分，我们给出了与银河系（MW）经历的主要并合事件动态关联的24个球状星团（GCs）的新年龄测定结果。我们利用深度且均匀的哈勃空间望远镜存档数据，应用CARMA等时线拟合代码，推导了与盖亚-香肠-恩克拉多斯（GSE）、人马座矮星系（Sag）、赫尔米流（H99）以及红杉星系（Seq）动态关联的系统的年龄、金属丰度、红化和距离模数的均匀估计值。这24个新测定结果补充了之前研究的11个GSE星团，以构建GSE系统的完整年龄-金属丰度关系（AMR）。我们发现每个原星系系统都呈现出明确的AMR，其斜率和范围反映了各自的恒星形成效率和化学增丰历史。通过在马尔可夫链蒙特卡洛框架内拟合解析AMR模型，我们量化了每个原星系的恒星质量和并合时间。这得到了首个严格来自均匀时间信息的详细并合树，据此，低能-克拉肯-赫拉克勒斯（LKH）系统是银河系经历的首个带来球状星团的并合事件，随后是红杉、H99、GSE，最后是Sgr。就恒星质量而言，最重要的事件是LKH、GSE和Sgr，它们总共贡献了约2.5×10^9太阳质量，对应银河系从足以容纳球状星团的大质量并合事件中吸积的恒星质量的95%以上。
英文摘要：
We present a new age determination of 24 globular clusters (GCs) dynamically associated with the main accretion events experienced by the Milky Way (MW), as part of the Cluster Ages to Reconstruct the Milky Way Assembly (CARMA) project's effort to trace the Galaxy's assembly history. We used deep and homogeneous archival Hubble Space Telescope data, and applied the CARMA isochrone-fitting code to derive homogeneous estimates of age, metallicity, reddening, and distance modulus for systems dynamically associated with Gaia-Sausage-Enceladus (GSE), the Sagittarius dwarf galaxy (Sag), the Helmi streams (H99), and the Sequoia galaxy (Seq). These 24 new determinations are supplemented by 11 previously studied GSE clusters to construct the complete age-metallicity relation (AMR) of the GSE system. We find that each progenitor system describes a well-defined AMR, with a distinct slope and extent reflecting its individual star-formation efficiency and chemical enrichment history. By fitting analytical AMR models within a Markov chain Monte Carlo framework, we quantify the stellar mass and accretion time for each progenitor galaxy. This results in the first detailed merger tree obtained from strictly homogeneous chronological information, according to which the Low-energy-Kraken-Heracles (LKH) system is the first merger experienced by the MW that brought GCs in, followed by Sequoia, H99, GSE, and finally Sgr. The most significant events in terms of stellar mass are LKH, GSE, and Sgr, which together contribute a total of approximately 2.5 x 10^9 solar masses. This corresponds to more than 95% of the stellar mass accreted by the MW from mergers massive enough to host GCs.
