The cosmic evolution of magnesium isotopes
The cosmic evolution of magnesium isotopes
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镁同位素的宇宙演化
DOI：
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发表时间：
2018
影响因子：
4.8
通讯作者：
K. A. Olive
中科院分区：
文献类型：
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作者：
E. Vangioni;K. A. Olive
星际介质中镁的丰度是宇宙时间尺度上恒星形成过程的强大探测器。镁有三种稳定的同位素：^24 mg、^25 mg和^26 mg，它们都可以在质量介于2到8 M_⊙之间的大质量和中等质量(IM)恒星中产生。在这项工作中，我们使用对宇宙恒星形成率密度(SFRD)的约束，并利用观测到的同位素比来探索IM星的作用和质量范围。我们比较了几种具有金属丰度相关产额的恒星核合成模型，并考虑了旋转对大质量恒星产额的影响及其对镁同位素演化的影响。我们使用了一个宇宙演化模型，该模型使用了新的观测SFRD数据和来自2018年普朗克合作确定的新的再电离约束。我们发现^24 mg的主要贡献来自大质量恒星，而^25 mg和^26 mg则来自IM星。为了对镁同位素比值的观测数据进行拟合，建议使用一个额外的IM SFRD组件。此外，当IM质量的范围向较大质量(5-8 M_⊙)缩小时，模型与数据之间的一致性进一步提高。虽然有些自转也改善了对数据的拟合，但我们可以排除所有恒星由于^26毫克的过剩而具有高自转速度的情况。
The abundance of magnesium in the interstellar medium is a powerful probe of star formation processes over cosmological time-scales. Magnesium has three stable isotopes, ^24Mg, ^25Mg, and ^26Mg, which can be produced in both massive and intermediate-mass (IM) stars with masses between 2 and 8 M_⊙. In this work, we use constraints on the cosmic star formation rate density (SFRD) and explore the role and mass range of IM stars using the observed isotopic ratios. We compare several models of stellar nucleosynthesis with metallicity-dependent yields and also consider the effect of rotation on the yields of massive stars and its consequences on the evolution of the Mg isotopes. We use a cosmic evolution model updated with new observational SFRD data and new reionization constraints coming from 2018 Planck Collaboration determinations. We find that the main contribution of ^24Mg comes from massive stars whereas ^25Mg and ^26Mg come from IM stars. To fit the observational data on magnesium isotopic ratios, an additional IM SFRD component is preferred. Moreover, the agreement between model and data is further improved when the range of IM masses is narrowed towards higher masses (5–8 M_⊙). While some rotation also improves the fit to data, we can exclude the case where all stars have high rotational velocities due to an overproduction of ^26Mg.