STEP调查：III. 云间阶梯：大麦哲伦桥的恒星形成历史
STEP survey: III. STEPping stones between the clouds: the star formation history of the Magellanic Bridge
AI总结：
研究通过STEP调查重建大麦哲伦桥的恒星形成历史，发现近期恒星形成峰值及低金属licity表明SMC气体剥离过程。
摘要：
大麦哲伦星云（MCs）为研究星系相互作用和矮星系演化提供了独特的实验室。通过研究恒星何时以及如何形成，恒星形成历史（SFH）是一种强有力的工具，可以为系统过去相互作用的动力学建模提供约束，并理解受潮汐影响环境中剥离和触发恒星形成的进程。我们旨在重建大麦哲伦桥的SFH，即连接两个星云的气体和恒星流。我们使用了深入的光学STEP调查数据，覆盖了54平方度的范围，包括小麦哲伦星云（SMC）和桥，探测到距离星云的最老主序转折点以下的恒星。我们应用了合成颜色-亮度图（CMD）技术来分析14平方度的STEP数据。我们基于PARSEC-COLIBRI和BaSTI恒星演化模型构建了两个合成恒星种群库，金属licity范围为-2.0≤[Fe/H]≤0，覆盖整个哈勃时间。我们发现大麦哲伦桥中存在一个明显的近期恒星形成峰值，约100Myr前，且向SMC方向逐渐增强。该种群的低金属licity表明，它是由SMC在最近一次与大麦哲伦星云（LMC）的近距离接触期间剥离的气体形成的。在桥的东侧（LMC侧），恒星形成峰值出现在更早的时间，大约在10Gyr和2Gyr前。我们估计桥中恒星总质量为(5.1±0.2)×10^5 M_⊙，当前恒星金属licity为[Fe/H]≈-0.6dex，接近SMC的值。
英文摘要：
The Magellanic Clouds (MCs) offer a unique laboratory for studying galaxy interaction and the evolution of dwarf galaxies. By investigating when and how stars formed, the star formation history (SFH) is a powerful tool to provide constraints for dynamical modeling of the system's past interactions and understand the processes of stripping and triggered star formation in tidally influenced environments. We aim to reconstruct the SFH of the Magellanic Bridge, the gaseous and stellar stream connecting the two Clouds. We used data from the deep optical STEP survey, which covers 54 $\mathrm{deg\, {^{2}}}$ across the Small Magellanic Cloud (SMC) and the Bridge, reaching stars below the oldest main sequence turnoff at the distance of the MCs. We applied the synthetic color-magnitude diagram (CMD) technique to 14 deg$^2$ of STEP data. We constructed two libraries of synthetic stellar populations based on the PARSEC-COLIBRI and BaSTI stellar evolutionary models, with metallicities in the range $-2.0\leq[$Fe/H$]\leq0$ across the whole Hubble time. We find a clear peak of recent star formation $\sim100$ Myr ago in the Magellanic Bridge, which becomes increasingly pronounced toward the SMC. The low metallicity of this population suggests that it formed from gas stripped from the SMC during its most recent close encounter with the LMC. In the eastern part of the Bridge (LMC side), the star formation peaks at earlier times, around 10 Gyr and 2 Gyr ago. We estimate a total stellar mass in the Bridge of $ (5.1 \pm 0.2) \times 10^5 M_\odot$ and a present-day stellar metallicity of $[$Fe/H$]\sim-0.6$ dex, close to SMC value.
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