SCYON Abstract

Received on June 28 2004

The Pleiades mass function : models versus observations

AuthorsE. Moraux (1), P. Kroupa (2), J.Bouvier (3)
(1) Institute of Astronomy, Cambridge, CB3 0HA, UK
(2) Sternwarte der Universität Bonn, Auf dem Hügel 71, D-53121 Bonn, Germany
(3) LAOG, B.P. 53, 38041 Grenoble Cedex 9, France
Accepted byAstronomy & Astrophysics
Links Pleiades


Two stellar-dynamical models of binary-rich embedded proto-Orion-Nebula-type clusters that evolve to Pleiades-like clusters are studied with an emphasis on comparing the stellar mass function with observational constraints. By the age of the Pleiades (about 100 Myr) both models show a similar degree of mass segregation which also agrees with observational constraints. This thus indicates that the Pleiades is well relaxed and that it is suffering from severe amnesia. It is found that the initial mass function (IMF) must have been indistinguishable from the standard or Galactic-field IMF for stars with mass < 2 Msun, provided the Pleiades precursor had a central density of about 104.8 stars/pc3. A denser model with 105.8 stars/pc3 also leads to reasonable agreement with observational constraints, but owing to the shorter relaxation time of the embedded cluster it evolves through energy equipartition to a mass-segregated condition just prior to residual-gas expulsion. This model consequently looses preferentially low-mass stars and brown dwarfs (BDs), but the effect is not very pronounced. The empirical data indicate that the Pleiades IMF may have been steeper than Salpeter for stars with > 2 Msun.