The formation times and building blocks of Milky Way-mass galaxies in the FIRE simulations
The formation times and building blocks of Milky Way-mass galaxies in the FIRE simulations
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DOI：
10.1093/mnras/staa1923
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发表时间：
2020-01
影响因子：
4.8
通讯作者：
I. Santistevan;A. Wetzel;K. El-Badry;J. Bland-Hawthorn;M. Boylan-Kolchin;J. Bailin;C. Faucher-Giguère-C.-Faucher
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文献类型：
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作者：
I. Santistevan;A. Wetzel;K. El-Badry;J. Bland-Hawthorn;M. Boylan-Kolchin;J. Bailin;C. Faucher-Giguère-C.-Faucher
对银河系（MW）和M31的调查使我们能够详细研究不同年龄和金属丰度的恒星种群，目标是重建整个宇宙时间的形成历史。这些调查激发了宇宙学背景下银河系考古学的关键问题：MW/M31质量星系的主要祖先是什么时候形成的，以及形成它的银河系积木是什么？利用Feedback In Realistic Environments-2宇宙学模拟研究了MW/M31质量星系的形成时间和祖星系，包括6个孤立的MW/M31质量星系和6个z = 0的类本星系群（LG）星系对.我们研究的主要祖“形成”的基础上两个指标：（1）从主要的非原位过渡到原位恒星质量增长和（2）质量优势相比，其他祖。我们发现，MW/M31质量星系的主要祖先通常出现在z = 3-4（11.6美元）。12.2\，\rm {Gyr}$ ago），而在z = 0的凸起区域（内部2 kpc）的恒星主要在z = 5（${\lesssim} \！12.6\，\rm {Gyr}$ ago）。与分离寄主相比，LG类配对寄主的主要祖细胞出现时间显著提前（Δz ≥ 2，$\Δ t\！sim \！1.6\，\rm {Gyr}$），在所有z <$4（${\gtrsim} \！12.2\，\rm {Gyr}$ ago）。这凸显了环境在MW/M31质量星系形成中的重要性，尤其是在早期。平均来说，大约有100个星系拥有$\rm {\it{ M}}_\rm {星星}\！\ gtrsim \！10^5\，\rm {M}_\odot$用于构建一个典型的MW/M31质量系统。因此，幸存的卫星代表了对祖先种群的高度不完整的普查（由105 ×）。
Surveys of the Milky Way (MW) and M31 enable detailed studies of stellar populations across ages and metallicities, with the goal of reconstructing formation histories across cosmic time. These surveys motivate key questions for galactic archaeology in a cosmological context: When did the main progenitor of an MW/M31-mass galaxy form, and what were the galactic building blocks that formed it? We investigate the formation times and progenitor galaxies of MW/M31-mass galaxies using the Feedback In Realistic Environments-2 cosmological simulations, including six isolated MW/M31-mass galaxies and six galaxies in Local Group (LG)-like pairs at z = 0. We examine main progenitor ‘formation’ based on two metrics: (1) transition from primarily ex-situ to in-situ stellar mass growth and (2) mass dominance compared to other progenitors. We find that the main progenitor of an MW/M31-mass galaxy emerged typically at z ∼ 3–4 ($11.6\!\!-\!\!12.2\, \rm {Gyr}$ ago), while stars in the bulge region (inner 2 kpc) at z = 0 formed primarily in a single main progenitor at z ≲ 5 (${\lesssim} \!12.6\, \rm {Gyr}$ ago). Compared with isolated hosts, the main progenitors of LG-like paired hosts emerged significantly earlier (Δz ∼ 2, $\Delta t\!\sim \!1.6\, \rm {Gyr}$), with ∼4× higher stellar mass at all z ≳ 4 (${\gtrsim} \!12.2\, \rm {Gyr}$ ago). This highlights the importance of environment in MW/M31-mass galaxy formation, especially at early times. On average, about 100 galaxies with $\rm {\it{ M}}_\rm {star}\!\gtrsim \!10^5\, \rm {M}_\odot$ went into building a typical MW/M31-mass system. Thus, surviving satellites represent a highly incomplete census (by ∼5×) of the progenitor population.