EDP Sciences
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Volume 426, Number 1, October IV 2004
Page(s) 75 - 80
Section Galactic structure, stellar clusters and populations
DOI http://dx.doi.org/10.1051/0004-6361:20035669

A&A 426, 75-80 (2004)
DOI: 10.1051/0004-6361:20035669

The Pleiades mass function: Models versus observations

E. Moraux1, 2, P. Kroupa3, 4, 5 and J. Bouvier1

1  Laboratoire d'Astrophysique, Observatoire de Grenoble, BP 53, 38041 Grenoble Cedex 9, France
2  Institut of Astronomy, Cambridge, CB3 0HA, UK
    e-mail: moraux@ast.cam.ac.uk
3  Institut für Theoretische Physik und Astrophysik der Universität Kiel, 24098 Kiel, Germany
4  Sternwarte der Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
5  Heisenberg Fellow

(Received 12 November 2003 / Accepted 23 June 2004 )

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 $m\lesssim 2\,M_\odot$, provided the Pleiades precursor had a central density of about 104.8 stars/pc 3. A denser model with 105.8 stars/pc 3 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 preferentially loses 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 the Salpeter for stars with $m\ga 2\,M_\odot$.

Key words: stars: low-mass, brown dwarfs -- stars: luminosity function, mass function -- Galaxy: open clusters and associations: general

© ESO 2004