发表机构
Kagoshima University; Kyushu Sangyo University; Konan University（鹿儿岛大学; 九州产业大学; 神户学院大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过沿磁流体模拟的密度和磁场历史进行尘埃演化计算，发现磁场延迟坍缩促进尘埃增长，影响电离、电阻率及红外散射，揭示磁控时标是连接这些过程的关键。
AI 中文摘要
对分子云中尘埃增长的研究通常预设坍缩历史，这使得磁场对核形成的调控如何塑造尘埃演化及其可观测和非理想磁流体动力学特征尚不清楚。我们通过沿从三维非理想磁流体动力学模拟中提取的、由纤维碎裂形成核的随时间变化的密度和磁场历史，进行单区尘埃演化和电离计算来解决这一问题。更强的初始磁场会延迟收缩，从而在给定密度下给予尘埃颗粒更多时间增长。在我们的模型中，这种延迟收缩导致在$n_{\mathrm{H}}=10^6\\,\mathrm{cm^{-3}}$时，对于$B_{\mathrm{ini}}=20$和$50\\,\mu\mathrm{G}$，质量加权平均尘埃尺寸分别为$1.2\\,\mu\mathrm{m}$和$3.1\\,\mu\mathrm{m}$。相关的极小尘埃颗粒的消耗减少了带电粒子在尘埃颗粒表面的吸附并降低了电导率：相对于没有尘埃增长的模型，电离分数从$\sim10^{-9}$增加到$\sim10^{-8}$，双极电阻率增加，离子-中性漂移速度在弱磁场模型中上升到几$\mathrm{m\\,s^{-1}}$，在强磁场模型中约为$10\\,\mathrm{m\\,s^{-1}}$。这些漂移速度仍低于观测建议的$30$--$100\\,\mathrm{m\\,s^{-1}}$范围，表明可能需要更强的磁场。演化的尘埃种群在$3.6$--$4.5\\,\mu\mathrm{m}$处也达到约$\omega_\lambda\sim0.8$的单次散射反照率，更强的磁场将高效红外散射的起始点移向更低密度。这些结果表明，磁控坍缩时标而非密度单独，将尘埃增长与电离、双极扩散和红外散射在前恒星核中联系起来。
英文摘要
Studies of dust growth in molecular clouds often prescribe the collapse history, leaving unclear how magnetic regulation of core formation shapes dust evolution and its observable and non-ideal MHD signatures. We address this problem by performing one-zone dust evolution and ionization calculations along time-dependent density and magnetic-field histories extracted from three-dimensional non-ideal MHD simulations of core formation through filament fragmentation. A stronger initial magnetic field delays contraction and thereby gives dust grains more time to grow at a given density. In our models, this delayed contraction leads to mass-weighted mean dust sizes of $1.2\,μ\mathrm{m}$ and $3.1\,μ\mathrm{m}$ at $n_{\mathrm{H}}=10^6\,\mathrm{cm^{-3}}$ for $B_{\mathrm{ini}}=20$ and $50\,μ\mathrm{G}$, respectively. The associated depletion of very small dust grains reduces the adsorption of charged particles onto dust grain surfaces and lowers the conductivity: relative to models without dust growth, the ionization fraction increases from $\sim10^{-9}$ to $\sim10^{-8}$, the ambipolar resistivity increases, and the ion--neutral drift velocity rises to several $\mathrm{m\,s^{-1}}$ in the weak-magnetic-field model and approximately $10\,\mathrm{m\,s^{-1}}$ in the strong-magnetic-field model. These drift velocities remain below the observationally suggested range of $30$--$100\,\mathrm{m\,s^{-1}}$, indicating that still stronger magnetic fields may be required. The evolved dust populations also attain single-scattering albedos of order $ω_λ\sim0.8$ at $3.6$--$4.5\,μ\mathrm{m}$, with the stronger field shifting the onset of efficient infrared scattering toward lower densities. These results demonstrate that the magnetically controlled collapse timescale, rather than density alone, links dust growth to ionization, ambipolar diffusion, and infrared scattering in prestellar cores.
CommentsAccepted for publication in The Astrophysical Journal
