FRIED: External photoevaporation of protoplanetary discs

我们对行星形成的理解在很大程度上受到距离太阳150pc内原行星盘观测的影响。它们的接近使它们最容易被发现和分辨，然而，这些圆盘实际上是非典型的。它们位于没有大质量恒星的稀疏星团中，因此辐射环境很弱。大多数恒星形成于大质量星团中，OB星发出丰富的紫外线辐射。这导致圆盘产生“外部光蒸发”（EP）风，导致它们的质量、半径和寿命迅速减少。因此，辐射环境可以控制恒星团中产生的系外行星，而这一点在我们对附近盘的关注中被忽略了。然而，理解紫外线环境的作用需要一个巨大的物理学和天体物理学链，从巨大的分子云和恒星形成，到分散盘的辐射流体动力学化学模型。如果没有必要的EP理论框架，我们就无法理解典型的行星形成。这一建议将建立这一理论框架。我们将开发最先进的3D辐射流体动力学和光解区域化学计算，以确定EP风在一系列紫外线环境中的结构和质量损失率。孤立地理解EP只是故事的一部分，内部风是由主星驱动的。我们将开发第一个内部和外部风之间相互作用的模型，以了解综合质量损失和观测意义。与恒星形成的联系也至关重要。随着时间的推移，恒星在星团中形成，并开始嵌入它们的生命，这可以保护光盘免受EP的影响。我们将确定巨大的分子云是如何坍缩的，以及云中的恒星反馈如何设定EP的作用。我们的理论模型将为观测项目提供预测。这项工作对于理解最常见的行星盘演化和行星形成场景是必要的。

Our understanding of planet formation is heavily influenced by observations of protoplanetary discs within 150pc of the Sun. Their proximity makes them easiest to detect and resolve, however, these discs are actually atypical. They are in sparse stellar clusters without massive stars, and so the radiation environment is weak. Most stars form in massive clusters, with OB stars that emit copious UV radiation. This drives "external photoevaporation" (EP) winds from discs, resulting in a rapid reduction of their mass, radius and lifetime. The radiation environment could hence control the resulting exoplanets in stellar clusters and this is being missed in our focus on nearby discs. However, understanding the role of UV environment requires a huge chain of physics and astrophysics, from giant molecular clouds and star formation, down to the radiation hydrodynamic chemical models of dispersing discs. We cannot understand typical planet formation without the necessary theoretical framework for EP, verified by observations. This proposal will establish that theoretical framework. We will develop new state of the art 3D radiation hydrodynamic and photodissociation region chemistry calculations to determine the structure and mass loss rate of EP winds in a range of UV environments. Understanding EP in isolation is just part of the story, with internal winds driven by the host star. We will develop the first models of the interplay between internal and external winds to understand the combined mass loss and observational implications. The connection to star formation is also vital. Stars form over time in clusters and begin their lives embedded, which can shield discs from EP. We will determine how giant molecular clouds collapse and stellar feedback in the cloud sets the role of EP. Our theoretical models will provide predictions to drive observational programs. This work is necessary for understanding the most common disc evolution and hence planet formation scenarios.