Brown dwarfs and rogue planets in star forming regions

能形成恒星的质量最低的物体是什么？在形成过程中，有多少大质量行星从它们的行星系统中被抛出？这两个问题将在这个项目中得到解决。在过去的几年里，我们在一个名为SONYC（邻近年轻星团中的恒星物体的简称）的项目中，对恒星形成区域中质量最低的自由漂浮物体进行了搜索。在SONYC中，我们使用现有最大的地面望远镜对天空中最年轻的星团进行超深度调查。虽然我们发现了大量的褐矮星（有一些有趣的证据表明褐矮星形成过程中的环境差异），但我们没有发现很多具有超级木星质量的物体，即被推测为被喷射的巨行星。如果它们存在（我们预计它们确实存在），它们的质量将低于我们设定的5倍木星质量的门槛，仍有待发现。在这个项目的下一步（以及这个博士项目）中，我们将使用詹姆斯韦伯太空望远镜探索质量在1到5木星质量之间的自由漂浮流浪行星领域。在2018年JWST开始运行后，我们很有可能获得观测时间来启动这个项目。学生将利用JWST和其他设施准备观察和探索后续途径，然后成为第一个分析数据的人。此外，我们将利用来自盖亚的第二份数据来确定年轻褐矮星的基本参数。这将导致对恒星形成模拟的新限制，并深入了解从恒星到行星形成的转变。这将是一个强烈的观测项目，它需要学习光学和红外观测的细节，超冷物体的物理学，从物体，磁盘和吸积中解开发射的复杂性，以及与理论方面的人合作的兴趣，包括大气物理学和恒星/行星形成。

What is the lowest mass object that can form like a star? And how many massive planets are ejected from their planetary systems during the formation process? These two questions will be tackled in this project. Over the last years, we have carried out a search for the lowest mass free-floating objects in star forming regions, in a project called SONYC (short for Substellar Objects in Nearby Young Clusters). In SONYC we used the largest existing ground-based telescopes to make ultradeep surveys of the youngest clusters on the sky. While we found plenty of brown dwarfs (with some interesting evidence for environmental difference in the formation of brown dwarfs), we did not find many objects with super-Jupiter masses, the presumed ejected giant planets. If they exist (and we expect that they do), they will be below our mass threshold of 5 Jupiter masses and are still to be discovered.In the next step of this project (and in this PhD project) we will use the James Webb Space Telescope to explore the domain of free-floating rogue planets with masses between 1 and 5 Jupiter masses. We have good chances to get observing time to get this project started right after the JWST begins operation in 2018. The student will prepare the observations and explore follow-up avenues, with JWST and other facilities, and then be the first to analyse the data. In addition, we will work with the second data release from Gaia to pin down the fundamental parameters of young brown dwarfs. This will lead to new contraints on star formation simulations and insights into the transition from star to planet formation.This will be a strongly observational project, which requires to learn the details of optical and infrared observations, the physics of ultracool objects, the intricacies of disentangling emission from objects, disks, and accretion, as well as an interest in collaborating with people from the theory side, including atmospheric physics and star/planet formation.