The formation mechanism of brown dwarfs

Matther R Bate, Ian Alexander Bonnell, Volker Bromm

Research output: Contribution to journalArticlepeer-review

266 Citations (Scopus)

Abstract

We present results from the first hydrodynamical star formation calculation to demonstrate that brown dwarfs are a natural and frequent product of the collapse and fragmentation of a turbulent molecular cloud. The brown dwarfs form via the fragmentation of dense molecular gas in unstable multiple systems and are ejected from the dense gas before they have been able to accrete to stellar masses. Thus, they can be viewed as 'failed stars'. Approximately three-quarters of the brown dwarfs form in gravitationally unstable circumstellar discs while the remainder form in collapsing filaments of molecular gas. These formation mechanisms are very efficient, producing roughly the same number of brown dwarfs as stars, in agreement with recent observations. However, because close dynamical interactions are involved in their formation, we find a very low frequency of binary brown dwarf systems (less than or similar to5 per cent) and that those binary brown dwarf systems that do exist must be close, less than or similar to10 au. Similarly, we find that young brown dwarfs with large circumstellar discs (radii greater than or similar to10 au) are rare (approximate to5 per cent).

Original languageEnglish
Pages (from-to)L65-L68
Number of pages5
JournalMonthly Notices of the Royal Astronomical Society
Volume332
Issue number3
DOIs
Publication statusPublished - May 2002

Keywords

  • accretion, accretion discs
  • hydrodynamics
  • binaries : general
  • circumstellar matter
  • stars : formation
  • stars : low-mass, brown dwarfs
  • SMOOTHED PARTICLE HYDRODYNAMICS
  • ROTATING INTERSTELLAR CLOUDS
  • DISC-DISC ENCOUNTERS
  • PROTOSTELLAR ENCOUNTERS
  • NUMERICAL SIMULATIONS
  • MOLECULAR CLOUD
  • STAR-FORMATION
  • MULTIPLE SYSTEMS
  • BINARY-SYSTEMS
  • MASS FUNCTION

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