FUV-Driven Photoevaporation of protoplanetary Disks

年轻的恒星被气体盘所包围，这些气体盘很可能是行星的诞生地。其中一个关键问题是：盘中有足够的尘埃和/或气体可供行星形成过程使用多久，这些物质的大部分将在哪里？观测估计产生的磁盘寿命为几百万年。这比经典的粘性吸积盘模型所能解释的要短得多，所以很明显，一定存在着某种主动破坏盘的过程。无论这个过程是什么，它都可能严重影响物质在盘中的分布，这是行星形成的一个关键问题，在观测上受到了不良的限制。在这个建议中，我们打算研究原行星盘被其自身的宿主星星光蒸发的过程作为盘的破坏机制。由EUV光子（13.6 - 100 eV）和来自宿主星星的X射线驱动的光蒸发现在已经相当好地理解了，但是由来自宿主星星的FUV光子（6 - 13.6 eV）驱动的蒸发仅仅是非常边缘的理解，因为它要复杂得多。然而，初步的工作表明，FUV驱动的光蒸发可能是占主导地位的机制。该提案的目标是通过开发这一过程的自洽数值模型来了解FUV驱动的光蒸发，以及它如何影响行星系统的这些摇篮中的物质分布。

Young stars are surrounded by gaseous disks which are the likely birthplaces of planets. One of the key questions is: How long will there be enough dust and/or gas in the disk available for the planet formation process, and where will most of this matter be? Observational estimates yield disk life times of a few million years. This is much shorter than classical viscous accretion disk models can explain, so clearly some process must exist that actively destroys the disk. Whatever this process is, it will likely severely affect the distribution of matter in the disk as well, a critical issue for planet formation that is observationally ill constrained. In this proposal we intend to study the process of photoevaporation of protoplanetary disks by their own host star as the disk destruction mechanism. Photoevaporation powered by EUV photons (13.6 - 100 eV) and X-rays from the host star is reasonably well understood nowadays, but evaporation powered by FUV photons (6 - 13.6 eV) from the host star is only very marginally understood because it is much more complex. Yet, preliminary work indicates that FUV-driven photoevaporation might be the dominant mechanism. The goal of this proposal is to understand FUV-driven photoevaporation by developing self-consistent numerical models of this process, and how it affects the matter distribution in these cradles of planetary systems.