Different processes have been proposed to explain the formation of S0s, including mergers, disc instabilities and quenched spirals. These processes are expected to dominate in different environments, and thus leave characteristic footprints in the kinematics and stellar populations of the individual components within the galaxies. New techniques enable us to cleanly disentangle the kinematics and stellar populations of these components in IFU observations. In this paper, we use buddi to spectroscopically extract the light from the bulge, disc and lens components within a sample of 8 S0 galaxies in extreme environments observed with MUSE. While the spectra of bulges and discs in S0 galaxies have been separated before, this work is the first to isolate the spectra of lenses. Stellar populations analysis revealed that the bulges and lenses have generally similar or higher metallicities than the discs, and the $\alpha$-enhancement of the bulges and discs are correlated, while those of the lenses are completely unconnected to either component. We conclude that the majority of the mass in these galaxies was built up early in the lifetime of the galaxy, with the bulges and discs forming from the same material through dissipational processes at high redshift. The lenses, on the other hand, formed over independent timescales at more random times within the lifetime of the galaxy, possibly from evolved bars. The younger stellar populations and asymmetric features seen in the field S0s may indicate that these galaxies have been affected more by minor mergers than the cluster galaxies.

中文翻译：

---

极端环境下 S0 的形成 II：凸起、圆盘和透镜的恒星形成历史

已经提出了不同的过程来解释 S0 的形成，包括合并、圆盘不稳定性和淬火螺旋。预计这些过程将在不同的环境中占主导地位，从而在星系内各个组成部分的运动学和恒星种群中留下特征足迹。新技术使我们能够在 IFU 观测中清楚地解开这些组件的运动学和恒星种群。在本文中，我们使用 buddi 以光谱方式从 MUSE 观察到的极端环境中的 8 个 S0 星系样本中的凸起、圆盘和透镜组件中提取光。虽然之前已经分离了 S0 星系中的凸起和圆盘的光谱，但这项工作是第一个分离透镜光谱的工作。恒星种群分析表明，凸起和透镜具有与圆盘相似或更高的金属丰度，并且凸起和圆盘的 $\alpha$ 增强是相关的，而透镜的那些与任一组件完全无关。我们得出的结论是，这些星系中的大部分质量是在星系生命周期的早期形成的，凸起和圆盘是通过高红移的耗散过程由相同材料形成的。另一方面，这些透镜是在星系生命周期内更随机的时间在独立的时间尺度上形成的，可能来自进化的酒吧。在 S0 视场中看到的年轻恒星种群和不对称特征可能表明这些星系比星团星系更容易受到轻微合并的影响。