arXiv 0705.36342007-05astro-ph

宇宙射线对星族III星形成的影响

Impact of Cosmic Rays on Population III Star Formation

Athena Stacy, Volker Bromm

备注：: MNRAS in press, 12 pages, 6 figures
DOI：: 10.1111/j.1365-2966.2007.12247.x

摘要：

我们探讨了可能的宇宙射线（CR）背景产生的第一次超新星爆炸，结束了大规模的第三星族恒星的短暂生命的影响。我们发现，如果CR通量足以在微晕中心附近产生大于10^-19 s^-1的电离率，那么这种CR背景可能会对红移约为z ~ 15 - 20的微晕中的原始气体云的冷却和坍缩产生显著影响。能量小于约10^7 eV的CR的存在将间接增强这些区域的分子冷却，我们估计这些微晕中由此产生的较低温度将产生低至约10 M太阳的特征恒星质量。在z ~ 10 - 15附近宇宙结构形成的后期阶段，CRs对更大质量的暗物质晕（维里质量大于约10^8 M_sun）内部的原始气体云的冷却和坍缩的影响不太明显。在这些云中，即使没有CR通量，分子丰度已经足够允许冷却到由宇宙微波背景温度设定的下限。

英文摘要：

We explore the implications of a possible cosmic ray (CR) background generated during the first supernova explosions that end the brief lives of massive Population III stars. We show that such a CR background could have significantly influenced the cooling and collapse of primordial gas clouds in minihaloes around redshifts of z ~ 15 - 20, provided the CR flux was sufficient to yield an ionization rate greater than about 10^-19 s^-1 near the center of the minihalo. The presence of CRs with energies less than approximately 10^7 eV would indirectly enhance the molecular cooling in these regions, and we estimate that the resulting lower temperatures in these minihaloes would yield a characteristic stellar mass as low as ~ 10 M_sun. CRs have a less pronounced effect on the cooling and collapse of primordial gas clouds inside more massive dark matter haloes with virial masses greater than approximately 10^8 M_sun at the later stages of cosmological structure formation around z ~ 10 - 15. In these clouds, even without CR flux the molecular abundance is already sufficient to allow cooling to the floor set by the temperature of the cosmic microwave background.

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