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arXiv 2406.09602astro-ph.GAastro-ph.SR
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大质量恒星附近的尘埃排空区：尘埃动力学对恒星形成区的影响

Dust-Evacuated Zones Near Massive Stars: Consequences of Dust Dynamics on Star-forming Regions

Nadine H. Soliman, Philip F. Hopkins, Michael Y. Grudić

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14 pages, 9 figures, submitted to ApJ
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AI总结：

本研究通过STARFORGE项目的辐射-尘埃-磁流体动力学模拟，发现大质量恒星辐射会排空周围尘埃形成抑制区，导致其及星周盘的吸积尘埃-气体比远低于母云，相关元素丰度出现显著偏差。

摘要：

恒星形成于分子云中由气体和尘埃共同构成的致密核内。然而，尽管尘埃在恒星形成过程中发挥着关键作用，其动力学特性却常被忽视，研究通常假设尘埃与气体的质量比以及颗粒尺寸谱是恒定且空间均匀的。本研究中，我们引入了一组来自STARFORGE（恒星形成锻造）项目的恒星形成分子云辐射-尘埃-磁流体动力学模拟。这些模拟在早期辐射磁流体动力学模型的基础上进行了扩展，原有模型已包含冷却、单颗恒星形成及反馈过程。值得注意的是，新模拟明确纳入了尘埃颗粒的动力学过程，考虑了作用于多种尺寸的活尘埃颗粒上的辐射力、阻力和洛伦兹力。我们发现，当恒星质量超过某一阈值（约2倍太阳质量$M_{\text{sun}}$）时，其发出的辐射可将周围的尘埃颗粒排空，形成尺寸约100天文单位（AU）的尘埃抑制区。尘埃通过冷却、化学作用、阻力和辐射转移与气体相互作用，其排空会改变该区域的气体性质。这一过程始于早期吸积阶段且早于主序阶段，会导致星周盘和恒星内部的吸积尘埃-气体（ADG）质量比出现随质量变化的耗减。我们预测，质量大于等于10倍太阳质量的大质量恒星，其ADG比会比其母分子云低约一个数量级。因此，恒星及其星盘、星周环境中，通常与尘埃颗粒相关的元素（如碳和氧）的丰度会出现显著偏差。

英文摘要：

Stars form within dense cores composed of both gas and dust within molecular clouds. However, despite the crucial role that dust plays in the star formation process, its dynamics is frequently overlooked, with the common assumption being a constant, spatially uniform dust-to-gas ratio and grain size spectrum. In this study, we introduce a set of radiation-dust-magnetohydrodynamic simulations of star forming molecular clouds from the {\small STARFORGE} project. These simulations expand upon the earlier radiation MHD models, which included cooling, individual star formation, and feedback. Notably, they explicitly address the dynamics of dust grains, considering radiation, drag, and Lorentz forces acting on a diverse size spectrum of live dust grains. We find that once stars exceed a certain mass threshold ($\sim 2 M_{\odot}$), their emitted radiation can evacuate dust grains from their vicinity, giving rise to a dust-suppressed zone of size $\sim 100$ AU. This removal of dust, which interacts with gas through cooling, chemistry, drag, and radiative transfer, alters the gas properties in the region. Commencing during the early accretion stages and preceding the Main-sequence phase, this process results in a mass-dependent depletion in the accreted dust-to-gas (ADG) mass ratio within both the circumstellar disc and the star. We predict massive stars ($\gtrsim 10 M_{\odot}$) would exhibit ADG ratios that are approximately one order of magnitude lower than that of their parent clouds. Consequently, stars, their discs, and circumstellar environments would display notable deviations in the abundances of elements commonly associated with dust grains, such as carbon and oxygen.

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