论文标题
Fornax3D项目：在Fornax集群星系NGC 1380和NGC 1427中发现古代大规模合并事件
The Fornax3D project: discovery of ancient massive merger events in the Fornax cluster galaxies NGC 1380 and NGC 1427
论文作者
论文摘要
我们报告了早期型星系NGC 1380和NGC 1427（Fornax Galaxy群集的成员）中古老的大规模合并事件的发现。 Muse IFU工具在VLT上观察到了两个星系，这是Fornax3D项目的一部分。通过将最近开发的种群 - 轨道叠加模型拟合到观察到的表面亮度以及恒星运动学，年龄和金属度图，我们获得了每个星系的恒星轨道，年龄和金属性分布。然后，我们将每个星系分解为基于轨道的多个组件，包括动态热的内部恒星光环分量，该组件被确定为过去大规模合并的遗物。通过与宇宙星系模拟中的类似物进行比较，主要是TNG50，我们发现这种炎热的内部恒星光环的形成需要与现已破坏的大型卫星星系合并为$ 3.7 _ _ { - 1.5}^{+2.7}^{+2.7} \ times 10^10^{10^{10} $ 1/5 $ 1/5 $ 1/5 $ 5 $ 5 $ 5 $ 5 $ 5 1380 and of $1.5_{-0.7}^{+1.6} \times10^{10}$ Msun (about $1/4$ of its current stellar mass) in the case of NGC 1427. Moreover, we infer that the last massive merger in NGC 1380 happened $\sim10$ Gyr ago based on the stellar age distribution of the re-grown dynamically cold disk, whereas the merger在NGC 1427中，基于其热恒星恒星光环中的恒星种群，以$ t \ Lessim 8 $ Gyr结束。 NGC 1380中的主要合并事件是第一个合并质量和合并时间的合并事件。此外，到目前为止，它是附近星系中最古老，最庞大的合并。
We report the discovery of ancient massive merger events in the early-type galaxies NGC 1380 and NGC 1427, members of the Fornax galaxy cluster. Both galaxies have been observed by the MUSE IFU instrument on the VLT, as part of the Fornax3D project. By fitting recently-developed population-orbital superposition models to the observed surface brightness as well as stellar kinematic, age, and metallicity maps, we obtain the stellar orbits, age and metallicity distributions of each galaxy. We then decompose each galaxy into multiple orbital-based components, including a dynamically hot inner stellar halo component which is identified as the relic of past massive mergers. By comparing to analogues from cosmological galaxy simulations, chiefly TNG50, we find that the formation of such a hot inner stellar halo requires the merger with a now-destroyed massive satellite galaxy of $3.7_{-1.5}^{+2.7} \times 10^{10}$ Msun (about $1/5$ of its current stellar mass) in the case of NGC 1380 and of $1.5_{-0.7}^{+1.6} \times10^{10}$ Msun (about $1/4$ of its current stellar mass) in the case of NGC 1427. Moreover, we infer that the last massive merger in NGC 1380 happened $\sim10$ Gyr ago based on the stellar age distribution of the re-grown dynamically cold disk, whereas the merger in NGC 1427 ended $t\lesssim 8$ Gyr ago based on the stellar populations in its hot inner stellar halo. The major merger event in NGC 1380 is the first one with both merger mass and merger time quantitatively inferred in a galaxy beyond the Local Volume. Moreover, it is the oldest and most massive merger uncovered in nearby galaxies so far.
