Dust in the Early Universe: Dust Formation in the Ejecta of Population III Supernovae
Dust in the Early Universe: Dust Formation in the Ejecta of Population III Supernovae
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DOI：
10.1086/379011
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发表时间：
2003-07
期刊：
影响因子：
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通讯作者：
T. Nozawa;T. Kozasa;H. Umeda;K. Maeda;K. Nomoto
中科院分区：
文献类型：
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作者：
T. Nozawa;T. Kozasa;H. Umeda;K. Maeda;K. Nomoto
尘埃颗粒在早期宇宙中恒星和星系的形成和演化历史中起着至关重要的作用。应用非稳态成核和颗粒生长理论，研究了星族III超新星（包括对不稳定超新星）的抛射物中尘埃颗粒的形成。尘埃形成的计算是对核心坍缩超新星进行的，其前身质量Mpr从13到30 M☉，以及对不稳定超新星的Mpr = 170和200 M☉。在计算中，考虑放射性元素的能量沉积，通过求解辐射传递方程，计算了喷射物中气体温度的时间演化，这对新形成颗粒的数量密度和大小有很大的影响。考虑了喷出物中元素组成的两种极端情况，即He核内未混合和均匀混合的情况，并假设CO和SiO分子的形成已经完成。核心坍缩超新星和对不稳定超新星的计算结果总结如下：在未混合的抛射物中，多种颗粒物质凝结，反映了抛射物中形成部位元素组成的差异；否则，在均匀混合的喷射物中只有氧化物颗粒凝结。根据晶粒种类和形成条件的不同，新形成晶粒的平均尺寸在3个数量级范围内，最大半径限制在1 μm以内，与原始质量无关。除了未混合的Mg硅酸盐、MgO、Si和FeS以及Al2O3外，各晶粒的尺寸分布函数近似为对数正态分布。所有颗粒种的粒径分布函数的求和近似为幂律公式，其指数为-3.5，大的为-3.5，小的为-2.5；根据超新星模型的不同，交点的半径在0.004 ~ 0.1 μm之间。锁定在尘埃颗粒中的质量比例随着祖恒星质量的增加而增加：核心坍缩超新星为祖恒星质量的2%-5%，对不稳定超新星为15%-30%，其祖恒星质量在140到260 M☉之间。因此，如果非常大质量的恒星占据了第一代恒星（星族III恒星），那么在早期宇宙中将产生大量的尘埃颗粒。我们还讨论了爆炸能量、喷出物中56Ni的含量以及CO和SiO分子的形成效率对超新星喷出物中尘埃颗粒形成的依赖性。
Dust grains play a crucial role in the formation and evolution history of stars and galaxies in the early universe. We investigate the formation of dust grains in the ejecta of Population III supernovae, including pair-instability supernovae, which are expected to occur in the early universe, applying a theory of non-steady state nucleation and grain growth. Dust formation calculations are performed for core-collapse supernovae with progenitor mass Mpr ranging from 13 to 30 M☉ and for pair-instability supernovae with Mpr = 170 and 200 M☉. In the calculations, the time evolution of gas temperature in the ejecta, which strongly affects the number density and size of newly formed grains, is calculated by solving the radiative transfer equation, taking account of the energy deposition of radioactive elements. Two extreme cases are considered for the elemental composition in the ejecta, unmixed and uniformly mixed cases within the He core, and formation of CO and SiO molecules is assumed to be complete. The results of calculations for core-collapse supernovae and pair-instability supernovae are summarized as follows: in the unmixed ejecta, a variety of grain species condense, reflecting the difference of the elemental composition at the formation site in the ejecta; otherwise only oxide grains condense in the uniformly mixed ejecta. The average size of newly formed grains spans a range of 3 orders of magnitude, depending on the grain species and the formation condition, and the maximum radius is limited to less than 1 μm, which does not depend on the progenitor mass. The size distribution function of each grain species is approximately lognormal, except for Mg silicates, MgO, Si, and FeS in the unmixed case and Al2O3 in both cases. The size distribution function summed up over all grain species is approximated by a power-law formula whose index is -3.5 for the larger radius and -2.5 for the smaller one; the radius at the crossover point ranges from 0.004 to 0.1 μm, depending on the model of supernovae. The fraction of mass locked into dust grains increases with increasing the progenitor mass: 2%-5% of the progenitor mass for core-collapse supernovae and 15%-30% for pair-instability supernovae whose progenitor mass ranges from 140 to 260 M☉. Thus, if very massive stars populated the first generation of stars (Population III stars), a large amount of dust grains would be produced in the early universe. We also discuss the dependence of the explosion energy and the amount of 56Ni in the ejecta, as well as the efficiency of formation of CO and SiO molecules, on the formation of dust grains in the ejecta of supernovae.