Where Are the Baryons? II. Feedback Effects
Where Are the Baryons? II. Feedback Effects
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DOI：
10.1086/506505
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发表时间：
2005-12
期刊：
影响因子：
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通讯作者：
R. Cen;J. Ostriker
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文献类型：
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作者：
R. Cen;J. Ostriker
对星系际介质的数值模拟表明，在当前时期，在（T ~ 106 K）温热的星系际介质（WHIM）中应该能发现相当一部分重子成分（40%~ 50%），最近的几个观测证据表明了这一预言的正确性。我们在这里重新计算的WHIM的演变与以下主要改进：（1）银河系和星星形成的银河系超风反馈过程被明确包括在内;（2）主要的金属物种（O V至O IX）的计算显式的非平衡方式;和（3）质量和空间动态范围分别由8和2倍，比我们以前的模拟大。以下是主要调查结果：（1）银河系的超级风具有戏剧性的影响，使WHIM的质量分数增加了约20%，主要是通过加热密度为平均密度101.5-104倍的星系附近的温暖气体。(2)WHIM中重子的比例比早期的工作略有增加，但仍然是~40%-50%。(3)WHIM的气体密度在平均密度的10-20倍的密度处广泛地达到峰值，范围从欠密度区域到过密度103-104的区域。(4)WHIM的中值金属丰度为0.18 Z，氧的50%和90%区间为（0.040，0.38）和（0.0017，0.83）。
Numerical simulations of the intergalactic medium have shown that at the present epoch, a significant fraction (40%-50%) of the baryonic component should be found in the (T ~ 106 K) warm-hot intergalactic medium (WHIM)—with several recent observational lines of evidence indicating the validity of the prediction. We here recompute the evolution of the WHIM with the following major improvements: (1) galactic superwind feedback processes from galaxy and star formation are explicitly included; (2) major metal species (O V to O IX) are computed explicitly in a nonequilibrium way; and (3) mass and spatial dynamic ranges are larger by factors of 8 and 2, respectively, than in our previous simulations. Here are the major findings: (1) Galactic superwinds have dramatic effects, increasing the WHIM mass fraction by about 20%, primarily through heating of warm gas near galaxies with density 101.5-104 times the mean density. (2) The fraction of baryons in the WHIM is increased modestly from the earlier work but is still ~40%-50%. (3) The gas density of the WHIM is broadly peaked at a density 10-20 times the mean density, ranging from underdense regions to regions that are overdense by 103-104. (4) The median metallicity of the WHIM is 0.18 Z☉ for oxygen, with 50% and 90% intervals being (0.040, 0.38) and (0.0017, 0.83).