SCYON Abstract

Received on December 9 2008

The influence of multiple stars on the high-mass stellar initial mass function and age-dating of young massive star clusters

AuthorsC. Weidner (1,2), P. Kroupa (3), and T. Maschberger (3,4)
Affiliation(1) Departamento de Astronomía y Astrofísica, Pontificia Universidad Católica de Chile, Santiago, Chile
(2) Scottish Universities Physics Alliance (SUPA), School of Pysics and Astronomy, University of St. Andrews, UK
(3) Argelander-Institut für Astronomie (Sternwarte), Auf dem Hügel 71, D-53121 Bonn, Germany
(4) Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, UK
Accepted byMonthly Notices of the Royal Astronomical Society
ContactCarsten.Weidner@st-andrews.ac.uk
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Abstract

The study of young stellar populations has revealed that most stars are in binary or higher order multiple systems. In this study the influence on the stellar initial mass function (IMF) of large quantities of unresolved multiple massive stars is investigated by taking into account stellar evolution an photometrically determined system masses. The models where initial masses are derived from the luminosity and colour of unresolved multiple systems show that even under extreme circumstances (100% binaries or higher order multiples) the difference between the power-law index of the mass function of all stars and the observed mass function is small (≤ 0.1). Thus, if the observed IMF has the Salpeter index α = 2.35 then the true stellar IMF has an index not flatter than α = 2.25. Additionally, unresolved multiple systems may hide between 15 and 60% of the underlying true mass of a star cluster. While already a known result, it is important to point out that the presence of a large number of unresolved binaries amongst pre-main-sequence (PMS) stars induces a significant spread in the measured ages of these stars even if there is none. Also, lower-mass stars in a single-age binary-rich cluster appear older than the massive stars by about 0.6 Myr.