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arXiv 1410.7861astro-ph.GA
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高红移尘埃类星体中粒度分布的演化:大量尘埃和不寻常消光曲线的积分

Evolution of grain size distribution in high-redshift dusty quasars: Integrating large amounts of dust and unusual extinction curves

Takaya Nozawa, Ryosuke S. Asano, Hiroyuki Hirashita, Tsutomu T. Takeuchi

摘要:

大量的尘埃和高红移类星体(z > 4)中不寻常的消光曲线的发现给早期宇宙尘埃的起源和性质带来了挑战性的问题。本文基于考虑颗粒尺寸分布的尘埃演化模型,研究了高Z类星体中尘埃含量和消光曲线的演化。首先,我们表明,牛奶路消光曲线是复制通过引入一个中等分数(~0.2)的致密的分子云相的星际介质的石墨-硅酸盐尘埃模型。然后,我们表明,在高z类星体中的消光曲线可以通过采取更高的分子云分数(>0.5)来解释,这导致更有效的晶粒生长和凝聚,并通过假设无定形碳而不是石墨。高Z类星体宿主中的大量尘埃含量也被发现是尘埃增长增强的自然结果。这些结果表明,分子云中的颗粒生长和凝聚是增加尘埃质量和改变星系中尘埃尺寸分布的关键过程,并且与不同的尘埃成分一起,可以有助于形成消光曲线。

英文摘要:

The discoveries of huge amounts of dust and unusual extinction curves in high-redshift quasars (z > 4) cast challenging issues on the origin and properties of dust in the early universe. In this Letter, we investigate the evolutions of dust content and extinction curve in a high-z quasar, based on the dust evolution model taking account of grain size distribution. First, we show that the Milky-Way extinction curve is reproduced by introducing a moderate fraction (~0.2) of dense molecular-cloud phases in the interstellar medium for a graphite-silicate dust model. Then we show that the peculier extinction curves in high-z quasars can be explained by taking a much higher molecular-cloud fraction (>0.5), which leads to more efficient grain growth and coagulation, and by assuming amorphous carbon instead of graphite. The large dust content in high-z quasar hosts is also found to be a natural consequence of the enhanced dust growth. These results indicate that grain growth and coagulation in molecular clouds are key processes that can increase the dust mass and change the size distribution of dust in galaxies, and that, along with a different dust composition, can contribute to shape the extinction curve.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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