The formation history of brown dwarfs and implications thereof on the low-mass initial mass function

关于褐矮星（BD）和极低质量恒星（VLMS）的性质和形成一直存在争议。虽然大多数观测小组将BD视为质量低于氢燃烧极限但具有恒星形成历史的恒星状物体，但有证据表明大多数BD和一些VLMS通过不同的机制形成。最引人注目的证据是观测证实的缺乏密切的BD同伴的恒星，所谓的褐矮星沙漠。此外，BD双星的轨道统计数据与恒星的轨道统计数据有很大的不同。一个可能的解释是，大质量的扩展的星周盘碎裂，随后从它们的诞生星星分离，从而形成了作为遥远恒星伴星的BD。在像猎户座星云团这样致密的恒星形成环境中，这样大的圆盘很可能会受到中等恒星碰撞的扰动。因此，现实的磁盘碎片化研究必须包括潮汐扰动的外部扩展磁盘。在这个计画中，我们将探讨棕矮星与恒星为不同族群时，对双星修正初始质量函数的影响。我们还旨在研究适度接近恒星形成的星团中的恒星-恒星相遇对磁盘碎片化的影响，以及BD的形成是否可能被抑制，甚至是由短时间尺度扰动引起的。

There is an ongoing debate about the nature and formation of brown dwarfs (BDs) and very-low-mass stars (VLMSs). While most observational groups treat BDs as star-like objects with masses below the hydrogen-burning limit but with a star-like formation history, there is evidence that most BDs and some VLMSs form via a different mechanism. The most striking evidence is the observationally confirmed lack of close BD companions to stars, the so-called brown dwarf desert. Furthermore, the orbital statistics of BD binaries differ significantly from those of stars. One possible explanation for this is the formation of BDs as distant stellar companions by fragmentation of massive extended circumstellar disks and subsequent separation from their birth star. In dense star-forming environments like the Orion Nebula Cluster such large disks are very likely to be perturbed by moderate star-star encounters. Realistic disk fragmentation studies must therefore include tidal perturbations of the outer parts of extended disks. In this project we will investigate the influence on the binary-corrected initial mass function if brown dwarfs and stars are different populations. We also aim to study the effects of moderately close star-star encounters in star-forming clusters on disk fragmentation, and whether the formation of BDs may be inhibited or even be induced by short-timescale perturbations.