论文标题
在球形几何形状中的原恒星塌陷模拟,灰尘凝血和碎片化
Protostellar collapse simulations in spherical geometry with dust coagulation and fragmentation
论文作者
论文摘要
我们使用新开发的鲨鱼代码对粉尘晶粒的凝结和碎片进行建模。它在球形几何形状和凝结/碎片方程中求解气体粉尘流体动力学。它还计算云的电离状态以及欧姆,双极和大厅的电阻率。我们发现,灰尘尺寸的分布在塌陷期间显着发展,大谷物形成由湍流差速度控制。当包括湍流时,只有双极性扩散在从分布中去除小晶粒方面仍然有效,布朗运动仅作为独立过程有效。宏观气体粉尘漂移可以忽略不计,对于晶粒的生长而言,只有在第一个拉尔森核心附近动态显着。在高密度下,我们发现凝结的分布不受灰尘分布的初始选择的影响。发现强磁场可增强小谷物的耗竭,从而导致双极扩散的重要增加。这暗示着磁场强度可以由原恒星塌陷期间的谷物种群调节。碎片化可能对裸硅酸盐有效,但其建模依赖于不受约束的参数的选择。还发现它对于冰冷的谷物而言可以忽略不计。当发生碎裂时,它会强烈影响磁性电阻率。灰尘凝血是一个关键过程,需要在原恒星崩溃期间完全考虑到。破碎的发作和反馈仍然不确定,应进一步研究其建模。
We model the coagulation and fragmentation of dust grains during the protostellar collapse with our newly developed shark code. It solves the gas-dust hydrodynamics in a spherical geometry and the coagulation/fragmentation equation. It also computes the ionization state of the cloud and the Ohmic, ambipolar and Hall resistivities. We find that the dust size distribution evolves significantly during the collapse, large grain formation being controlled by the turbulent differential velocity. When turbulence is included, only ambipolar diffusion remains efficient at removing the small grains from the distribution, brownian motion is only efficient as a standalone process. The macroscopic gas-dust drift is negligible for grain growth and only dynamically significant near the first Larson core. At high density, we find that the coagulated distribution is unaffected by the initial choice of dust distribution. Strong magnetic fields are found to enhance the small grains depletion, causing an important increase of the ambipolar diffusion. This hints that the magnetic field strength could be regulated by the small grain population during the protostellar collapse. Fragmentation could be effective for bare silicates, but its modeling relies on the choice of ill-constrained parameters. It is also found to be negligible for icy grains. When fragmentation occurs, it strongly affects the magnetic resistivities profiles. Dust coagulation is a critical process that needs to be fully taken into account during the protostellar collapse. The onset and feedback of fragmentation remains uncertain and its modeling should be further investigated.