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以内的原行星盘的观测的影响。它们的接近使它们最容易检测和解决，然而，这些磁盘实际上是非典型的。它们位于稀疏星团中，没有大质量恒星，因此辐射环境很弱。大多数恒星都是以大质量星团的形式形成的，OB恒星会发出大量的紫外线辐射。这驱动了来自圆盘的“外部光蒸发”(EP)风，导致它们的质量、半径和寿命迅速减小。因此，辐射环境可以控制星团中产生的系外行星，而这一点在我们对附近圆盘的关注中被遗漏了。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，从巨型分子云和恒星形成，到分散盘的辐射流体动力学化学模型。如果没有经过观测证实的EP的必要理论框架，我们就无法理解典型的行星形成。这项提议将建立这一理论框架。我们将开发最新的3D辐射流体动力学和光解离区化学计算，以确定在一系列UV环境中EP风的结构和质量损失率。孤立地理解EP只是故事的一部分，内在的风是由主持人明星驱动的。我们将开发第一个内风和外风相互作用的模型，以了解综合质量损失和观测意义。与恒星形成的联系也是至关重要的。恒星随着时间的推移形成星团，并开始嵌入它们的生命，这可以保护圆盘免受EP的伤害。我们将确定巨型分子云如何崩塌，以及星云中的恒星反馈如何设定EP的角色。我们的理论模型将为推动观测计划提供预测。这项工作对于理解最常见的圆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.