Effects of metal enrichment and metal cooling in galaxy growth and cosmic star formation history
Effects of metal enrichment and metal cooling in galaxy growth and cosmic star formation history
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金属富集和金属冷却对星系生长和宇宙恒星形成历史的影响
DOI：
10.1111/j.1365-2966.2008.14297.x
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发表时间：
2008
影响因子：
4.8
通讯作者：
K. Nagamine
中科院分区：
文献类型：
--
作者：
Jun;K. Nagamine
利用宇宙流体动力学模拟方法，对金属富集和金属冷却对星系形成和宇宙星星形成（SF）历史的影响进行了数值研究。我们发现，与没有金属冷却的模拟相比，有金属冷却的模拟有以下不同：（i）宇宙星星的形成率在z = 1和3时分别提高了约50%和20%;（ii）星系中的气体质量分数较低;（3）重子总质量函数（气体+星星）在z = 3处没有显著差异，但在z = 1时，相对大质量星系的数量增加;（4）星系际介质（IGM）的重子质量分数在z <3由于更有效的冷却和气体吸积到星系。我们的研究结果表明，金属冷却通过两种不同的机制增强了星系的生长：（i）增加在本地星际介质中的SF效率和（ii）增加IGM吸积星系。前一个过程在宇宙历史的大部分时间里都是有效的，而后一个过程只在z < 3时有效，此时IGM由于反馈而被金属充分富集。
We present the results of a numerical study on the effects of metal enrichment and metal cooling on galaxy formation and cosmic star formation (SF) history using cosmological hydrodynamic simulations. We find the following differences in the simulation with metal cooling when compared to the run without it: (i) the cosmic star formation rate is enhanced by about 50 and 20 per cent at z = 1 and 3, respectively; (ii) the gas mass fraction in galaxies is lower; (iii) the total baryonic mass function (gas + star) at z = 3 does not differ significantly, but shows an increase in the number of relatively massive galaxies at z = 1 and (4) the baryonic mass fraction of intergalactic medium (IGM) is reduced at z < 3 due to more efficient cooling and gas accretion on to galaxies. Our results suggest that the metal cooling enhances the galaxy growth by two different mechanisms: (i) increase in SF efficiency in the local interstellar medium and (ii) increase in IGM accretion on to galaxies. The former process is effective throughout most of the cosmic history, while the latter is effective only at z < 3 when the IGM is sufficiently enriched by metals owing to feedback.