Probing Formation from Stars to Planets: Accretion, Binarity and Disks in Young Brown Dwarfs

在过去的15年里，太阳系外行星的发现是天文学史上最重要的进步之一。到目前为止，已经发现了300多个恒星系统结构，小到几个地球质量。确定这些行星(以及那些质量较低的行星将在未来几年被探测到)的形成机制、性质和宜居性是当前天体物理研究的前沿。这些问题反过来又与恒星形成的基本问题密切相关，因为行星是由吸积盘形成的，吸积盘是恒星形成过程的整体结果，并最终决定了最终的恒星质量。最后，恒星和行星的形成和性质都与褐矮星密切相关：棕矮星是横跨恒星和行星之间的质量范围的恒星下天体，两者都有许多共同的特征。在这个项目中，我通过回答三个广泛的问题来研究恒星、棕矮星和行星的相互关联的起源：1)年轻的恒星和棕矮星是如何从它们周围的吸积盘中吸积物质的？2)棕矮星是如何形成的？3)行星能围绕棕矮星形成吗？这项研究需要各种观测技术，从高分辨率光谱学和光谱偏振学到使用自适应光学的分辨率成像，部署的波长范围从光学到亚毫米，并结合理论分析和数值模拟使用地面和天基设施。该项目的结果应该提供一个从恒星到行星质量的物理过程的广泛和全面的图景，这些过程一直是天体形成的基础。

The discovery of extrasolar planets over the last decade and a half ranks among the most important advances in the history of astronomy. More than three hundred have been found so far, in a plethora of stellar system architectures, and down to a few Earth masses. Determining the formation mechanism, properties and habitability of these planets (and those of lower mass bound to be detected in coming years) is at the cutting edge of current astrophysical research. These questions are in turn intimately linked to the fundamental issue of star formation, since planets form out of the accretion disks that are an integral outcome of the star-formation process and that ultimately determine the final stellar mass. Finally, the formation and properties of both stars and planets are closely tied to those of brown dwarfs: substellar bodies that straddle the mass range between stars and planets and share many features with both. In this project, I investigate the inter-linked origins of stars, brown dwarfs and planets by addressing 3 broad questions: 1) How do young stars and brown dwarfs accrete material from their surrounding accretion disks? 2) How do brown dwarfs form? 3) Can planets form around brown dwarfs? The research entails a variety of observational techniques, from high-resolution spectroscopy and spectropolarimetry to resolved imaging with adaptive optics, deployed over wavelengths ranging from the optical to sub-millimetre and using both ground- and space-based facilities, allied with theoretical analysis and numerical modeling. The results of the project should provide a broad and comprehensive picture of the physical processes that underlie the formation of objects all the way from from stellar down to planetary masses.