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arXiv 1502.07369astro-ph.EP
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尘埃演化和光蒸发对星盘扩散的影响

The Impact of Dust Evolution and Photoevaporation on Disk Dispersal

Uma Gorti, David Hollenbach, Cornelis Dullemond

摘要:

原行星盘在几百万年内由于粘性演化和光蒸发而分散;在此期间,小的、亚微米尺寸的尘埃颗粒必须生长并形成行星。在一个不断发展的磁盘中的小颗粒的随时间变化的丰度直接影响气体加热的远紫外光子,而尘埃演变影响光蒸发通过改变磁盘的不透明度和导致的渗透FUV光子在磁盘中。光蒸发流,反过来,选择性地携带小的尘埃颗粒离开较大的颗粒-从气体中分离-在磁盘后面。我们研究这些影响,通过调查的磁盘的粘度,光蒸发的EUV,FUV和X射线,尘埃演化,和径向漂移使用1-D多流体的方法(气体+不同的尘埃粒度)来解决不断变化的表面密度分布的演变。1-D的演变增加了1+1D模型构建在每个时代,以获得瞬时磁盘结构,并确定光蒸发率。尘埃凝聚/碎裂模型的实施结果在磁盘寿命的边际减少相比,没有灰尘演变的模型,磁盘的寿命,因此被发现是相对不敏感的不断变化的尘埃不透明度。我们发现,光蒸发可以导致显着减少的气体/尘埃的质量比在行星形成区域的磁盘,因为它的演变,并可能导致相应的增加重元素丰度相对于氢。我们讨论了星子形成和巨型行星形成理论的影响,包括形成的气体贫巨人。在气盘分散之后,固体中质量的$\sim 3\times 10^{-4}$ \ms \通常保留下来,与我们太阳系的固体存量相当。

英文摘要:

Protoplanetary disks are dispersed by viscous evolution and photoevaporation in a few million years; in the interim small, sub-micron sized dust grains must grow and form planets. The time-varying abundance of small grains in an evolving disk directly affects gas heating by far-ultraviolet photons, while dust evolution affects photoevaporation by changing the disk opacity and resulting penetration of FUV photons in the disk. Photoevaporative flows, in turn, selectively carry small dust grains leaving the larger particles---which decouple from the gas---behind in the disk. We study these effects by investigating the evolution of a disk subject to viscosity, photoevaporation by EUV, FUV and X-rays, dust evolution, and radial drift using a 1-D multi-fluid approach (gas + different dust grain sizes) to solve for the evolving surface density distributions. The 1-D evolution is augmented by 1+1D models constructed at each epoch to obtain the instantaneous disk structure and determine photoevaporation rates. The implementation of a dust coagulation/fragmentation model results in a marginal decrease in disk lifetimes when compared to models with no dust evolution; the disk lifetime is thus found to be relatively insensitive to the evolving dust opacity. We find that photoevaporation can cause significant reductions in the gas/dust mass ratio in the planet-forming regions of the disk as it evolves, and may result in a corresponding increase in heavy element abundances relative to hydrogen. We discuss implications for theories of planetesimal formation and giant planet formation, including the formation of gas-poor giants. After gas disk dispersal, $\sim 3\times 10^{-4}$ \ms\ of mass in solids typically remain, comparable to the solids inventory of our solar system.

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