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

褐矮星的形成历史及其对低质量初始质量函数的影响

基本信息

批准号：
160547581
负责人：
Professor Dr. Pavel Kroupa
金额：
--
依托单位：
Helmholtz-Institut für Strahlen- und Kernphysik
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2010
资助国家：
德国
起止时间：
2009-12-31 至 2014-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/160547581?language=en
关键词：
formation history brown dwarfs implications

项目摘要

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.

关于褐矮星(BDS)和极低质量恒星(VLMS)的性质和形成，人们一直在争论。虽然大多数观测组织认为BDS是质量低于氢气燃烧极限但具有类似恒星形成历史的类似恒星的天体，但有证据表明，大多数BDS和一些VLMS是通过不同的机制形成的。最明显的证据是观测证实缺乏与恒星关系密切的BD伴星，即所谓的棕矮星沙漠。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不同。一种可能的解释是，BDS作为遥远的恒星伴侣，是通过大量延伸的星盘碎裂并随后与它们的诞生恒星分离而形成的。在像猎户座星云星团这样密集的恒星形成环境中，如此大的圆盘很可能会受到中等恒星-恒星相遇的干扰。因此，现实的磁盘碎裂研究必须包括扩展磁盘外部的潮汐扰动。在这个项目中，我们将研究如果棕矮星和恒星是不同的种群，对双星修正的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星-星相遇对盘片碎裂的影响，以及短时间尺度扰动是否会抑制甚至诱导BDS的形成。