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

关于褐矮星（BDs）和极低质量恒星（VLMSs）的性质和形成一直存在争论。虽然大多数观测小组将北斗系统视为质量低于氢燃烧极限的类恒星物体，但具有类恒星的形成历史，但有证据表明，大多数北斗系统和一些VLMSs的形成机制不同。最引人注目的证据是观测证实缺乏与恒星密切的双子星伴星，即所谓的褐矮星沙漠。此外，双星的轨道统计与恒星的轨道统计有很大的不同。一种可能的解释是，BDs作为遥远的恒星伴星的形成，是由于大质量扩展的星周盘的碎片和随后与它们的诞生恒星分离而形成的。在像猎户座星云团这样密集的恒星形成环境中，如此大的圆盘很可能受到中等恒星与恒星相遇的干扰。因此，现实的磁盘碎片研究必须包括扩展磁盘外部部分的潮汐扰动。在这个项目中，我们将研究棕矮星和恒星是不同种群时对二元校正初始质量函数的影响。我们还旨在研究恒星形成星团中中等距离的恒星-恒星相遇对磁盘碎片的影响，以及短时间尺度的扰动是否可以抑制甚至诱导bd的形成。

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.