标题： 宇宙化学演化 显示英文标题

标题： Cosmic Chemical Evolution

摘要： 数值模拟标准宇宙学情景现在已经达到了足够的复杂程度，可以对基本问题提供初步答案：重元素是在哪里以及何时形成的？ 整体平均来看，这些模拟给出的金属量从$z=3$时的太阳值的1%增加到现在的20%。 事实上，这个结论具有误导性，因为它掩盖了金属量对局部密度的强烈依赖性。 在每一个时期，高密度区域的金属量都远高于低密度区域。 此外，最高密度区域很快接近太阳金属量并达到饱和，而更典型的区域则缓慢跟上。 这些结果比许多人的简单观点（即金属量随时间逐渐、近似均匀地增加）更符合观测数据。 显示英文摘要

摘要： Numerical simulations of standard cosmological scenarios have now reached the degree of sophistication required to provide tentative answers to the fundamental question: Where and when were the heavy elements formed? Averaging globally, these simulations give a metallicity that increases from 1% of the solar value at $z=3$ to 20% at present. This conclusion is, in fact, misleading, as it masks the very strong dependency of metallicity on local density. At every epoch higher density regions have much higher metallicity than lower density regions. Moreover, the highest density regions quickly approach near solar metallicity and then saturate, while more typical regions slowly catch up. These results are much more consistent with observational data than the simpler picture (adopted by many) of gradual, quasi-uniform increase of metallicity with time.