Cosmic Chemical Evolution Based on the Hierarchical Galaxy Formation Scenario

贫金属恒星的氧铁丰度比提供了大质量恒星核合成产量的信息，这些大质量恒星以II型超新星爆炸告终。利用银河系化学演化的标准模型，我们重现了太阳邻域丰度数据，并估计了真正的SN II起源的氧和铁产量。将估计的产率与理论产率进行比较，得出每一代恒星的质量下限和质量上限与IMF斜率之间的关系。在此关系之外，我们进一步从太阳附近的恒星质量光比推导出质量下限与IMF斜率之间的关系。这些独立关系明确地确定了m<@D2u@>D2=50（]SY.+-）的质量上限。() 10 M < @D2 (SY.sun。[)@>D2和IMF斜率指数1.3-1.6 M以上<@D2(] sys .sun.[)@>D2。这个质量上限对应的质量超过了这个质量，恒星就会以黑洞的形式结束，而不会将加工过的物质喷射到星际介质中。我们还发现，IMF斜率指数低于0.5 M<@D2(]SY.sun。[)@>D2不能比0.8浅太多。

Oxygen to iron abundance ratios of metal-poor stars provide information on nucleosynthesis yields from massive stars which end in Type II supernova explosions. Using a standard model of chemical evolution of the Galaxy we have reproduced the solar neighborhood abundance data and estimated the oxygen and iron yields of genuine SN II origin. The estimated yields are compared with the theoretical yields to derive the relation between the lower and upper mass limits in each generation of stars and the IMF slope. Independently of this relation, we furthermore derive the relation between the lower mass linit and the IMF slope from the stellar mass to light ratio in the solar neighborhood. These independent relations unambiguously determine the upper mass limit of m<@D2u@>D2=50(]SY.+-。[)10 M<@D2(]SY.sun.[)@>D2 and the IMF slope index of 1.3-1.6 above 1 M<@D2(]SY.sun.[)@>D2. This upper mass limit corresponds to the mass beyond which stars end as black holes without ejecting processed matter into the interstellar medium. we also find that the IMF slope index below 0.5 M<@D2(]SY.sun.[)@>D2 cannot be much shallower than 0.8.