Early chemical enrichment of the universe and the role of very massive population III stars
Early chemical enrichment of the universe and the role of very massive population III stars
复制标题
宇宙的早期化学富集和超大质量星族 III 恒星的作用
DOI：
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
F. Calura
中科院分区：
文献类型：
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作者：
F. Matteucci;F. Calura
本文讨论了超大质量星族III （pop III）在早期宇宙化学富集中的作用。我们首先将我们的预测与高红移Lyman-a森林测量的丰度比进行比较，以检查它们是否与假设早期宇宙由大质量pop III恒星丰富所预测的值相容。我们得出结论，为了解释在星系间介质中观测到的C/Si比率，pop II恒星对碳富集的贡献是必要的，已经在红移z = 5。然后，我们评估了将宇宙富集到临界金属丰度zcr所需的对不稳定超新星（SNyy）的数量，即导致从非常大质量恒星状态（m > 100 m〇）过渡到较低质量状态的金属丰度值，类似于当前的一个特征（m < 100 m〇）。。我们发现，在110到115 sny之间，对于各种初始质量函数，足以在高红移的星系间介质中化学富集一个立方兆秒差距。通过计算这些SN γγ和pop III恒星提供的电离光子的数量，我们得出结论，没有足够的光子来再电离宇宙，至少减少了约3倍。最后，我们计算了pop III恒星产生的丰度比，并将其与低金属丰度阻尼Lyman-a系统（DLAs）中观测到的丰度比进行了比较。我们认为，pop III星不能单独对这些天体的丰度比率负责，中等质量的pop II星一定在使dla富集氮方面发挥了重要作用。
In this paper the role of very massive population III (pop III) stars in the chemical enrichment of the early universe is discussed. We first compare our predictions with the abundance ratios measured in the high-redshift Lyman-a forest to check whether they are compatible with the values predicted by assuming that the early universe was enriched by massive pop III stars. We conclude that to explain the observed C/Si ratio in the intergalactic medium, a contribution from pop II stars to carbon enrichment is necessary, already at redshift z = 5. We then evaluate the number of pair-instability supernovae (SNyy) required to enrich the universe to the critical metallicity Z cr , i.e. the metallicity value which causes the transition from a very massive star regime (m > 100 M ○. ) to a lower mass regime, similar to the one characteristic of the present time (m < 100 M ○. ). It is found that between 110 and 115 SNyy are sufficient to chemically enrich a cubic megaparsec of the intergalactic medium at high redshift for a variety of initial mass functions. The number of ionizing photons provided by these SN γγ and also by the pop III stars ending as black holes was computed and we conclude that there are not enough photons to reionize the universe, being down by at least a factor of ∼3. Finally, we calculate the abundance ratios generated by pop III stars and compare them with the ones observed in low-metallicity damped Lyman-a systems (DLAs). We suggest that pop III stars alone cannot be responsible for the abundance ratios in these objects and that intermediate mass pop II stars must have played an important role especially in enriching DLAs in nitrogen.