AI 中文总结
研究宇宙尘埃颗粒生长效率，通过分子动力学模拟非晶碳颗粒表面受气相原子撞击情况，发现高附着系数，实验结果也支持该结论，证实气相吸积是星际尘埃质量增长的有效机制及星际颗粒演化核心。
AI 中文摘要
宇宙尘埃是星际介质的固相，传统上认为由碳质和硅酸盐颗粒组成，尺寸范围约为5 Å至1μm。尘埃虽仅占星际介质质量的最多1%，但对星系可观测特性的重要性仅次于恒星。颗粒生长效率的巨大不确定性模糊了宇宙中两种主要尘埃来源的相对贡献。超级计算机的进步使我们能够通过原子动力学计算超越简单理想化的尘埃颗粒生长效率预测。我们表明，小碳尘埃颗粒能在比宇宙年龄短得多的时间尺度上显著生长，在某些星际介质阶段，与巨分子云的寿命相当。具体而言，我们在现实星际条件下对受宇宙丰富元素气相原子撞击的非晶碳颗粒表面进行分子动力学模拟，发现所有相关气体和颗粒温度下，所有非惰性元素的附着系数都很高（≥0.2）。我们展示了在类似尘埃候选材料上进行的实验结果，支持我们的理论计算。因此，我们的结果证实，气相物质在颗粒上的吸积过程可能是星际尘埃质量在天体物理时间尺度上增长的有效机制，并且可能是所有宇宙时期星际颗粒演化生命周期的核心。
英文摘要
Cosmic dust is the solid phase of the interstellar medium (ISM), classically assumed to be composed of carbonaceous and silicate grains with size distributions spanning $\sim 5~Å$ to $\sim 1~μ$m (Weingartner & Draine 2001, Draine & Li 2007, Hensley & Draine 2023). While it constitutes at most order-of-magnitude $\mathbf{1\%}$ of the ISM mass, dust is second only to stars in importance for the observable properties of galaxies (Zavala et al. 2021). Large uncertainties in the efficiency of grain growth obfuscate the relative contribution of the two dominant sources of dust in the Universe: direct production from evolved stars versus gas-phase accretion in the ambient ISM (Feldmann 2015, Esmerian & Gnedin 2022, Esmerian & Gnedin 2024). Advances in supercomputers have only recently allowed us to move beyond simple, idealized predictions of dust grain growth efficiencies (Leitch-Devlin & Williams 1985) with atomistic dynamical calculations (Bossion et al. 2024). We show that small carbon dust grains can grow significantly on timescales much shorter than the age of the universe and, in some ISM phases, comparable to the lifetimes of giant molecular clouds. Specifically, we perform molecular dynamics simulations of an amorphous carbon (a-C) grain surface impacted by gas-phase atoms of cosmologically abundant elements with realistic interstellar conditions, finding high ($\gtrsim 0.2$) sticking coefficients for all non-inert elements at all relevant gas and grain temperatures. We present the results of experiments conducted on similar dust candidate materials that support our theoretical calculations. Our results therefore confirm that the process of gas-phase accretion onto grains is likely an efficient mechanism for the growth of interstellar dust mass on astrophysical timescales, and plausibly central to the evolutionary life-cycle of interstellar grains at all cosmic epochs. (abridged)
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