Open AccessSubstellar companions and isolated planetary‐mass objects from protostellar disc fragmentation
Author(s) -
Rice W. K. M.,
Armitage P. J.,
Bonnell I. A.,
Bate M. R.,
Jeffers S. V.,
Vine S. G.
Publication year - 2003
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2003.07317.x
Subject(s) - physics , astrophysics , brown dwarf , planet , astronomy , planetary mass , planetary system , accretion (finance) , metallicity , gas giant , stars , exoplanet
Self‐gravitating protostellar discs are unstable to fragmentation if the gas can cool on a time‐scale that is short compared with the orbital period. We use a combination of hydrodynamic simulations and N ‐body orbit integrations to study the long‐term evolution of a fragmenting disc with an initial mass ratio to the star of M disc / M * = 0.1 . For a disc that is initially unstable across a range of radii, a combination of collapse and subsequent accretion yields substellar objects with a spectrum of masses extending (for a Solar‐mass star) up to ≈0.01 M ⊙ . Subsequent gravitational evolution ejects most of the lower mass objects within a few million years, leaving a small number of very massive planets or brown dwarfs in eccentric orbits at moderately small radii. Based on these results, systems such as HD 168443 – in which the companions are close to or beyond the deuterium burning limit – appear to be the best candidates to have formed via gravitational instability. If massive substellar companions originate from disc fragmentation, while lower‐mass planetary companions originate from core accretion, the metallicity distribution of stars which host massive substellar companions at radii of ∼1 au should differ from that of stars with lower mass planetary companions.