演化巨分子云中~（26）Al和~（60）Fe的衰变
Abundance of 26Al and 60Fe in evolving Giant Molecular Clouds
摘要：
放射性$^{26}$ Al（t $_{1/2} \sim$ 0.72\，Myr）和$^{60}$ Fe，（t $_{1/2} \sim$ 2.5\，Myr）的核合成和向星际介质中的喷射受大质量恒星的星风和超新星II型爆炸的支配。对陨石及其成分的研究表明，这些短寿命放射性核素在太阳原行星盘中的初始丰度高于从$γ$ -射线天文学和银河系化学演化模型推断的银河系背景水平。这一观测结果被用来论证恒星碎片在太阳系的母体分子云或太阳原行星盘的后期阶段增加，因此我们的太阳系的形成需要一个特殊的情景。在这里，我们使用超级计算机模型-从第一原理-生产，运输和混合的新鲜合成的$^{26}$铝和$^{60}$铁在巨大的分子云内的恒星形成区域。在典型的恒星形成条件下，大多数恒星形成区域的$^{26}$ Al水平与从陨石中推断的水平相当，这表明在早期太阳系中存在短寿命放射性核素是巨型分子云化学演化的一般特征。从我们的模拟计算的$^{60}$ Fe/ $^{26}$ Al屈服比的$\approx 0.2$是一致的银河值0.15 $\pm$ 0.06推断从$γ$ -射线天文学，但显着高于大多数目前的太阳系测量表明。我们认为，估计的基础上分化的陨石和一些陨石成分可能不代表最初的$^{60}$铁丰度的散装太阳系。
英文摘要：
The nucleosynthesis and ejection of radioactive $^{26}$Al (t$_{1/2} \sim$ 0.72\,Myr) and $^{60}$Fe, (t$_{1/2} \sim$ 2.5\,Myr) into the interstellar medium is dominated by the stellar winds of massive stars and supernova type II explosions. Studies of meteorites and their components indicate that the initial abundances of these short-lived radionuclides in the solar protoplanetary disk were higher than the background levels of the galaxy inferred from $γ$--ray astronomy and models of the galactic chemical evolution. This observation has been used to argue for a late-stage addition of stellar debris to the Solar System's parental molecular cloud or, alternatively, the solar protoplanetary disk, thereby requiring a special scenario for the formation of our Solar System. Here, we use supercomputers to model---from first principles---the production, transport and admixing of freshly synthesized $^{26}$Al and $^{60}$Fe in star-forming regions within giant molecular clouds. Under typical star-formation conditions, the levels of $^{26}$Al in most star-forming regions are comparable to that deduced from meteorites, suggesting that the presence of short-lived radionuclides in the early Solar System is a generic feature of the chemical evolution of giant molecular clouds. The $^{60}$Fe/$^{26}$Al yield ratio of $\approx 0.2$ calculated from our simulations is consistent with the galactic value of 0.15 $\pm$ 0.06 inferred from $γ$--ray astronomy but is significantly higher than most current Solar System measurements indicate. We suggest that estimates based on differentiated meteorites and some chondritic components may not be representative of the initial $^{60}$Fe abundance of the bulk Solar System.
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