A relationship between stellar metallicity gradients and galaxy age in dwarf galaxies
A relationship between stellar metallicity gradients and galaxy age in dwarf galaxies
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矮星系中恒星金属丰度梯度与星系年龄之间的关系
DOI：
10.1093/mnras/staa3958
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发表时间：
2021
影响因子：
4.8
通讯作者：
Faucher-Giguère, Claude-André
中科院分区：
文献类型：
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作者：
Mercado, Francisco J;Bullock, James S;Boylan-Kolchin, Michael;Moreno, Jorge;Wetzel, Andrew;El-Badry, Kareem;Graus, Andrew S;Fitts, Alex;Hopkins, Philip F;Faucher-Giguère, Claude-André
我们在模拟和观测的矮小星系中探索了恒星金属丰度梯度的来源。我们使用了对26个孤立星系的FIRE-2宇宙重子放大模拟，以及对10个局部群矮小星系的现有观测数据。我们模拟的星系的恒星质量在105.5到108.6米⊙之间。虽然在我们模拟的星系中，气相金属丰度梯度通常很弱，但我们发现恒星的金属丰度梯度是常见的，中心区域往往比外部更富金属。梯度的强度与整个星系的中值恒星年龄相关，因此具有较年轻恒星群的星系具有更平坦的梯度。恒星的金属度梯度是由两个相互竞争的过程设定的：(1)反馈驱动的势能涨落使古老的贫金属星稳定地“膨胀”；(2)晚期延展的富金属气体的积累，这为晚期富金属星的形成提供了燃料。如果新近形成的恒星占主导地位，那么扩展的、富含金属的恒星形成会冲刷掉先前存在的“喷发”过程中的梯度。我们利用已发表的来自10个局部群矮星系的结果表明，在真正的矮星中，年龄与恒星金属丰度-梯度强度之间存在类似的关系。这表明，观测到的恒星金属丰度梯度可能主要是由重子/反馈循环驱动的，而不是由外部环境影响驱动的。
We explore the origin of stellar metallicity gradients in simulated and observed dwarf galaxies. We use FIRE-2 cosmological baryonic zoom-in simulations of 26 isolated galaxies as well as existing observational data for 10 Local Group dwarf galaxies. Our simulated galaxies have stellar masses between 105.5and 108.6M⊙. Whilst gas-phase metallicty gradients are generally weak in our simulated galaxies, we find that stellar metallicity gradients are common, with central regions tending to be more metal-rich than the outer parts. The strength of the gradient is correlated with galaxy-wide median stellar age, such that galaxies with younger stellar populations have flatter gradients. Stellar metallicty gradients are set by two competing processes: (1) the steady ‘puffing’ of old, metal-poor stars by feedback-driven potential fluctuations and (2) the accretion of extended, metal-rich gas at late times, which fuels late-time metal-rich star formation. If recent star formation dominates, then extended, metal-rich star formation washes out pre-existing gradients from the ‘puffing’ process. We use published results from ten Local Group dwarf galaxies to show that a similar relationship between age and stellar metallicity-gradient strength exists among real dwarfs. This suggests that observed stellar metallicity gradients may be driven largely by the baryon/feedback cycle rather than by external environmental effects.