Formation and early evolution of gas giants: The accretion shock and its consequences

最近的观测工作已经开始通过直接成像技术揭示离恒星很远的年轻和明亮的气体巨星。由于它们的年轻，这些物体的亮度仍然反映了它们形成的条件和塑造它们的物理过程。甚至最近，一些系统已经被发现，我们正在目睹气体巨星的持续形成，正如吸积签名所揭示的那样。然而，这些令人兴奋的探测结果的问题在于，从光度推断质量是必须的，但这些模型目前在早期是不受约束的。人们认为，决定行星光度的最重要因素是行星表面的辐射吸积激波。极端的结果分别导致热启动和冷启动，其中行星以高或低的光度开始其形成后的冷却。这些差异的光度是巨大的，至关重要的是，一直阻碍了可靠的测定mass.Therefore，我们建议进行第一个现实的研究行星吸积冲击进行二维辐射流体动力学模拟详细的微观物理。我们将把重点放在行星表面的吸积区域，以确定冲击后的条件以及冲击的效率，即，入射动能中作为辐射损失的部分。鉴于磁层吸积图像，我们也将包括磁场的影响。这些结果将使我们能够预测气体巨星形成后的光度，并为模拟（嵌入式）吸积行星的观测外观及其在盘上的热化学反馈提供输入。这项研究被设计为一系列扩展和联合收割机现有工具的较小任务。鉴于不久的将来会直接探测到，这使得拟议的研究成为一个低风险、高影响的项目。

Recent observational efforts have started to reveal a population of young and bright gas giants at large distances from their stars through the technique of direct imaging. Because of their youth, the brightness of these objects still reflects the conditions of their formation and the physical processes that shape them. Even more recently, a few systems have been discovered in which we are witnessing the ongoing formation of gas giants, as revealed by accretion signatures. The issue with these exciting detections, however, is that models are necessary to infer masses from the luminosities but that these models are currently unconstrained at early times.What is thought to be the single most important element setting a planet's luminosity is the radiative accretion shock at the surface of the planet. The extreme outcomes lead to hot and cold starts, respectively, in which the planet begins its post-formation cooling with a high or low luminosity. These differences in luminosity are colossal and, critically, have been hampering a reliable determination of the masses.Therefore, we propose to conduct the first realistic study of the planet accretion shock by performing two-dimensional radiation-hydrodynamical simulations with detailed microphysics. We will focus on the accretion region at the surface of the planet to determine the post-shock conditions as well as the efficiency of the shock, i.e., the fraction of the incoming kinetic energy which is lost as radiation. In view of the magnetospheric-accretion picture, we will also include the effects of a magnetic field. These results will enable us to predict the luminosity of gas giants after their formation and as well as to provide input to simulations of the observational appearance of (embedded) accreting planets and their thermo-chemical feedback on the disk.This research is designed as a series of smaller tasks which extend and combine existing tools. In view of near-future direct detections, this makes the proposed research a low-risk, high-impact project.