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

• Applicant: Professor Dr. Pavel Kroupa
• Subject Area: Astrophysics and Astronomy
• Term: from 2010 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 160547581

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.

• DFG Programme: Research Grants