The origins of the circumgalactic medium in the FIRE simulations
The origins of the circumgalactic medium in the FIRE simulations
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DOI：
10.1093/mnras/stz1773
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发表时间：
2018-11
影响因子：
4.8
通讯作者：
Zachary Hafen;C. Faucher-Giguère;D. Anglés-Alcázar;J. Stern;D. Keres̆;C. Hummels;C. Esmerian;S. Garrison-Kimmel;K. El-Badry;A. Wetzel;T. K. Chan;P. Hopkins;N. Murray
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文献类型：
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作者：
Zachary Hafen;C. Faucher-Giguère;D. Anglés-Alcázar;J. Stern;D. Keres̆;C. Hummels;C. Esmerian;S. Garrison-Kimmel;K. El-Badry;A. Wetzel;T. K. Chan;P. Hopkins;N. Murray
我们使用粒子追踪分析来研究环星系介质（CGM）的起源，将其分为（1）来自星系际介质（IGM）的吸积，（2）来自中央星系的风，和（3）来自其他星系的气体喷射。我们的样本由21个FIRE-2模拟组成，跨越晕质量范围Mh 1010-1012 M，我们专注于z = 0.25和z = 2。由于强烈的恒星反馈，只有重子晕保持重子质量$\gtrsim\！50\hbox{percent}$的宇宙预算。金属被晕圈更有效地保留，保留分数为$\gtrsim\！50\hbox{percent}$。在所有的质量和红移分析$\gtrsim \！CGM质量的60%源自IGM吸积（其中一些与下落晕有关）。总的来说，第二个最重要的贡献是来自中央星系的风，尽管从卫星上喷出或剥离的气体可以在1000亿升的日冕中贡献相当的质量。气体可以在CGM中持续数十亿年，导致混合良好的晕气体。因此，通过CGM的视线可能会与多种来源的气体相交。对于低红移的星系晕，冷气体（T < 104.7 K）平均优先沿着星系平面分布，但具有很强的晕到晕的变化。IGM吸积的金属丰度是系统低于风的金属丰度（通常由101 dex），虽然CGM和IGM金属丰度显着依赖于次网格金属扩散的治疗。我们的研究结果突出了多种物理机制，有助于CGM，并将通知观测工作，以制定一个有凝聚力的图片。
We use a particle tracking analysis to study the origins of the circumgalactic medium (CGM), separating it into (1) accretion from the intergalactic medium (IGM), (2) wind from the central galaxy, and (3) gas ejected from other galaxies. Our sample consists of 21 FIRE-2 simulations, spanning the halo mass range Mh ∼ 1010–1012 M⊙, and we focus on z = 0.25 and z = 2. Owing to strong stellar feedback, only ∼L⋆ haloes retain a baryon mass $\gtrsim\! 50\hbox{ per cent}$ of their cosmic budget. Metals are more efficiently retained by haloes, with a retention fraction $\gtrsim\! 50\hbox{ per cent}$. Across all masses and redshifts analysed $\gtrsim \!60\hbox{ per cent}$ of the CGM mass originates as IGM accretion (some of which is associated with infalling haloes). Overall, the second most important contribution is wind from the central galaxy, though gas ejected or stripped from satellites can contribute a comparable mass in ∼L⋆ haloes. Gas can persist in the CGM for billions of years, resulting in well mixed-halo gas. Sightlines through the CGM are therefore likely to intersect gas of multiple origins. For low-redshift ∼L⋆ haloes, cool gas (T < 104.7 K) is distributed on average preferentially along the galaxy plane, however with strong halo-to-halo variability. The metallicity of IGM accretion is systematically lower than the metallicity of winds (typically by ≳1 dex), although CGM and IGM metallicities depend significantly on the treatment of subgrid metal diffusion. Our results highlight the multiple physical mechanisms that contribute to the CGM and will inform observational efforts to develop a cohesive picture.