Dust formation in early galaxies
Dust formation in early galaxies
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DOI：
10.1046/j.1365-8711.2003.06681.x
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发表时间：
2003-02
影响因子：
4.8
通讯作者：
H. Morgan;M. Edmunds
中科院分区：
文献类型：
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作者：
H. Morgan;M. Edmunds
我们调查了早期星系中尘埃的来源和数量。我们讨论尘埃成核恒星大气中使用已发表的扩展大气模型，恒星演化轨道和成核条件。中等质量恒星的热脉动渐近巨星分支阶段很可能是恒星风中尘埃形成的最有希望的场所。我们提出了一个基本模型，包括尘埃形成的时间尺度，其中星际介质中的尘埃量是由化学演化。高红移星系模型的影响进行了研究，我们表明，没有困难，在产生尘埃星系的红移超过5，如果超新星是星际尘埃的主要来源。如果尘埃不能在超新星中有效凝结，那么只有具有高星星形成效率的星系才能在z > 5处产生大量尘埃质量。这与深亚毫米波普通用户测辐射热阵列调查中发现的亚毫米波源所暗示的高星星形成率是一致的。我们发现，在很低的金属丰度（1/100太阳）的分子云的质量半径指数小于2的情况下，单个恒星形成云的可见光深度可以达到大于1的值。在早期宇宙中，如果尘埃存在，大部分来自星星形成的辐射将以红外波长出现。然而，通过一个典型的早期星系的（斑片状）视觉光学深度将保持平均小于1，直到金属丰度达到1/10太阳。
We investigate the sources and amount of dust in early galaxies. We discuss dust nucleation in stellar atmospheres using published extended atmosphere models, stellar evolution tracks and nucleation conditions. The thermally pulsating asymptotic giant branch phase of intermediate-mass stars is likely to be the most promising site for dust formation in stellar winds. We present an elementary model including dust formation time-scales in which the amount of dust in the interstellar medium is governed by chemical evolution. The implications of the model for high-redshift galaxies are investigated and we show there is no difficulty in producing dusty galaxies at redshifts above 5 if supernovae are a dominant source of interstellar dust. If dust does not condense efficiently in supernovae then significant dust masses can only be generated at z > 5 by galaxies with a high star formation efficiency. This is consistent with the high star formation rates implied by submillimetre sources found in deep Submillimetre Common User Bolometric Array surveys. We find the visual optical depth for individual star-forming clouds can reach values greater than 1 at very low metallicity (1/100 solar) provided that the mass–radius exponent of molecular clouds is less than 2. Most of the radiation from star formation will emerge at infrared wavelengths in the early Universe provided that dust is present. The (patchy) visual optical depth through a typical early galaxy will, however, remain less than 1 on average until a metallicity of 1/10 solar is reached.