The In Situ Origins of Dwarf Stellar Outskirts in FIRE-2
The In Situ Origins of Dwarf Stellar Outskirts in FIRE-2
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DOI：
10.3847/1538-4357/ac6c88
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发表时间：
2021-09
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影响因子：
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通讯作者：
Erin Kado-Fong;R. Sanderson;J. Greene;E. Cunningham;Coral Wheeler;T. K. Chan;K. El-Badry;P. Hop
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文献类型：
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作者：
Erin Kado-Fong;R. Sanderson;J. Greene;E. Cunningham;Coral Wheeler;T. K. Chan;K. El-Badry;P. Hop
在观测到的宇宙中，大质量矮小星系(108.5<；M⋆/M⊙<；109.6)周围似乎普遍存在着延长的、古老的和圆形的恒星晕。然而，这些矮星不太可能经历了足够多的微小合并，形成了主要由吸积恒星组成的恒星晕。在这里，我们证明了FIRE-2(现实环境中的反馈)宇宙学放大模拟能够产生具有真实结构的矮星系，包括厚盘和圆形恒星晕。至关重要的是，这些恒星晕是在原地形成的，主要是通过盘状恒星向外迁移形成的。然而，在FIRE-2中也存在大量的“非盘状”矮星，它们缺乏明确的圆盘/晕，与观测到的矮星种群并不相似。这些非盘状矮星往往要么比盘状矮星更缺乏气体，要么具有比盘状矮星更具爆发性的近期恒星形成历史，这表明恒星形成反馈可能正在阻止圆盘形成。这两类矮星都强调了星系的内在形状--它是对星系恒星含量分布的直接量化--在模拟星系中询问反馈执行情况的力量。
Extended, old, and round stellar halos appear to be ubiquitous around high-mass dwarf galaxies (108.5 < M ⋆/M ⊙ < 109.6) in the observed universe. However, it is unlikely that these dwarfs have undergone a sufficient number of minor mergers to form stellar halos that are composed of predominantly accreted stars. Here, we demonstrate that FIRE-2 (Feedback in Realistic Environments) cosmological zoom-in simulations are capable of producing dwarf galaxies with realistic structures, including both a thick disk and round stellar halo. Crucially, these stellar halos are formed in situ, largely via the outward migration of disk stars. However, there also exists a large population of “nondisky” dwarfs in FIRE-2 that lack a well-defined disk/halo and do not resemble the observed dwarf population. These nondisky dwarfs tend to be either more gas-poor or to have burstier recent star formation histories than the disky dwarfs, suggesting that star formation feedback may be preventing disk formation. Both classes of dwarfs underscore the power of a galaxy’s intrinsic shape—which is a direct quantification of the distribution of the galaxy’s stellar content—to interrogate the feedback implementation in simulated galaxies.