We present a novel scenario for the growth of dust grains in galaxies at high redshift (z ∼ 6). In our model, the mechanical feedback from massive star clusters evolving within high-density pre-enriched media allows to pile up a large amount of matter into massive supershells. If the gas metallicity (≥Z⊙), number density (≥106 cm−3), and dust-to-gas mass ratio (∼1/150 × Z) within the supershell are sufficiently large, such supershells may become optically thick to the starlight emerging from their host star clusters and even to radiation from the cosmic microwave background (CMB). Based on semi-analytic models, we argue that this mechanism, occurring in the case of massive (${\ge} 10^7\, {\rm M}_{\odot }$) molecular clouds hosting ${\ge} 10^6\, {\rm M}_{\odot }$ star clusters, allows a large mass of gas and dust to acquire a temperature below that of the CMB, whereupon dust grain growth may occur with ease. In galaxies with total stellar mass M*, grain growth within supershells may increase the dust mass by ${\sim} 10^6\, {\rm M}_{\odot } (M_{*}/10^{8}\, {\rm M}_{\odot })$.

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高红移下的尘粒生长：星暴驱动的 CMB 暗超级壳

我们提出了一种新的场景，用于在高红移（z∼6）的星系中尘埃颗粒的生长。在我们的模型中，大质量星团在高密度预富集介质中演化的机械反馈允许将大量物质堆积成大质量超级壳。如果超级壳内的气体金属丰度 (≥Z⊙)、数密度 (≥106 cm-3) 和尘气质量比 (∼1/150 × Z) 足够大，则此类超级壳可能会变得光学厚至从它们的主星团中发出的星光，甚至来自宇宙微波背景（CMB）的辐射。基于半解析模型，我们认为这种机制发生在大规模 (${\ge} 10^7\, {\rm M}_{\odot }$) 分子云托管 ${\ge} 10^6\, {\rm M}_{\odot }$ 星团，允许大量气体和尘埃获得低于 CMB 的温度，因此尘埃颗粒的生长很容易发生。在总恒星质量为 M* 的星系中，超级壳内的颗粒生长可能会使尘埃质量增加 ${\sim} 10^6\, {\rm M}_{\odot } (M_{*}/10^{8} \, {\rm M}_{\odot })$。