SCYON Abstract

Received on October 5 2009

The relation between the most-massive star and its parental star cluster mass

AuthorsC. Weidner (1,2), P. Kroupa (3), and I.A.D. Bonnell (1)
Affiliation(1) Scottish Universities Physics Alliance (SUPA), School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9SS, UK
(2) Departamento de Astronomia y Astrofisica, Pontificia Universidad Catolica de Chile, Av. Vicuna MacKenna 4860, Macul, Santiago, Chile
(3) Argelander-Institut für Astronomie (Sternwarte), Auf dem Hügel 71, D-53121 Bonn, Germany
Accepted byMonthly Notices of the Royal Astronomical Society
ContactCarsten.Weidner@st-andrews.ac.uk
URLhttp://arxiv.org/abs/0909.1555
Links

Abstract

We present a thorough literature study of the most-massive star, m_max, in several young star clusters in order to assess whether or not star clusters are populated from the stellar initial mass function (IMF) by random sampling over the mass range 0.01 < m < 150 M(sun) without being constrained by the cluster mass, Mecl. The data reveal a partition of the sample into lowest mass objects (Mecl < 102 M(sun)), moderate mass clusters (102 M(sun) < Mecl < 103 M(sun)) and rich clusters above 103 M(sun). Additionally, there is a plateau of a constant maximal star mass (mmax ~ 25 M(sun)) for clusters with masses between 103 M(sun) and 4x103 M(sun). Statistical tests of this data set reveal that the hypothesis of random sampling from the IMF between 0.01 and 150 M(sun) is highly unlikely for star clusters more massive than 102 M(sun) with a probability of p ~ 2x10-7 for the objects with Mecl between 102 M(sun) and 103 M(sun) and p ~ 3x10-9 for the more massive star clusters. Also, the spread of m_max values at a given Mecl is smaller than expected from random sampling. We suggest that the basic physical process able to explain this dependence of stellar inventory of a star cluster on its mass may be the interplay between stellar feedback and the binding energy of the cluster-forming molecular cloud core. Given these results, it would follow that an integrated galactic initial mass function (IGIMF) sampled from such clusters would automatically be steeper in comparison to the IMF within individual star clusters.