论文标题
快速消除分子云中的小尘土
Rapid Elimination of Small Dust Grains in Molecular Clouds
论文作者
论文摘要
我们认为，尺寸小于$ \ sim 0.1 $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $的分子云核的冲击速度由双层扩散引起的漂移主导。这种效果是由于粉尘耦合到磁场和中性气体的尺寸依赖性所致。假设完美地坚持碰撞最高约50美元m/s，我们表明，这种效果会导致小晶粒的快速消耗 - 与星光灭绝和IR/微波排放测量一致，既在核心中心（$ n \ sim 10^{6} $ cm $ cm $ $ $ $^{ - 3} $）和$ nvelope（$ nvelope（$ nvelope）（ cm $^{ - 3} $）。如果仅考虑这种效果产生的速度，大小分布的上端不会显着变化。我们考虑了进化的灰尘尺寸分布对气温的影响，并认为，如果像我们的模型那样发生小尘土谷物的耗竭，那么宇宙射线电离速率必须低于$ 10^{ - 16} $ s $ s $ s $ s $^{ - 1} $，以$ 10^{5} $ cm $ cm $ cm $ cm $ cm $ cm $ cm $ cm $^}的数量密度为$ 10^{5}。
We argue that impact velocities between dust grains with sizes less than $\sim 0.1$ $μm$ in molecular cloud cores are dominated by drift arising from ambipolar diffusion. This effect is due to the size dependence of the dust coupling to the magnetic field and the neutral gas. Assuming perfect sticking in collisions up to $\approx 50$ m/s, we show that this effect causes rapid depletion of small grains - consistent with starlight extinction and IR/microwave emission measurements, both in the core center ($n \sim 10^{6}$ cm$^{-3}$) and envelope ($n \sim 10^{4}$ cm$^{-3}$). The upper end of the size distribution does not change significantly if only velocities arising from this effect are considered. We consider the impact of an evolved dust size distribution on the gas temperature, and argue that if the depletion of small dust grains occurs as would be expected from our model, then the cosmic ray ionization rate must be well below $10^{-16}$ s$^{-1}$ at a number density of $10^{5}$ cm$^{-3}$.
