微晕中Virialized气体的低金属富集
Lower Metal Enrichment of Virialized Gas in Minihalos
摘要：
我们区分金属富集的气体在维里化的迷你晕和星系际介质在高红移，宇宙学再电离有关，与最初的期望，气体在高密度区域内形成的暗物质晕可能更强大，从而抵抗与低密度星系际介质混合。作为一个例子，我们对小晕中的气体云进行了详细的流体动力学模拟，发现对于速度为10- 100 km/s的实际激波，小晕中rho>500 rhob的高密度气体中有90%以上（65%）在质量z=10处维里化（10^7，10^6）Msun的金属丰度仍然低于星系际介质的3%，红移z=6。可以预期，当它们被纳入更大的晕中时，小晕中的高密度气体成为随后恒星形成的燃料，在那里有效的原子冷却可以诱导气体冷凝，从而形成恒星。由于小晕在高红移时会维里化，而此时宇宙并没有显著的再电离，这意味着维里化的小晕中的气体可能提供了丰富的原始气体库，从而可能允许第三族无金属恒星的形成延伸到比基于星系际介质富集的其他预期低得多的红移。
英文摘要：
We differentiate between the metal enrichment of the gas in virialized minihalos and that of the intergalactic medium at high redshift, pertinent to cosmological reionization, with the initial expectation that gas in the high density regions within formed dark matter halos may be more robust thus resistant to mixing with lower density intergalactic medium. Using detailed hydrodynamic simulations of gas clouds in minihalos subject to destructive processes associated with the encompassing intergalactic shocks carrying metal-enriched gas, we find, as an example, that, for realistic shocks of velocities of 10-100km/s, more than (90%,65%) of the high density gas with rho>500 rhob inside a minihalo virialized at z=10 of mass (10^7,10^6)Msun remains at a metallicity lower than 3% of that of the intergalactic medium by redshift z=6. It may be expected that the high density gas in minihalos becomes fuel for subsequent star formation, when they are incorporated into larger halos where efficient atomic cooling can induce gas condensation hence star formation. Since minihalos virialize at high redshift when the universe is not expected to have been significantly reionized, the implication is that gas in virialized minihalos may provide an abundant reservoir of primordial gas to possibly allow for the formation of Population-III metal-free stars to extend to much lower redshift than otherwise expected based on the enrichment of intergalactic medium.
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