Journal Article

Accretion-driven core collapse and the collisional formation of massive stars

C. J. Clarke and I. A. Bonnell

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 388, issue 3, pages 1171-1174
Published in print August 2008 | ISSN: 0035-8711
Published online July 2008 | e-ISSN: 1365-2966 | DOI:
Accretion-driven core collapse and the collisional formation of massive stars

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We consider the conditions required for a cluster core to shrink, by adiabatic accretion of gas from the surrounding cluster, to densities such that stellar collisions are a likely outcome. We show that the maximum densities attained, and hence the viability of collisions, depend on the balance between core shrinkage (driven by accretion) and core puffing up (driven by relaxation effects). The expected number of collisions scales as , where Ncore is the number of stars in the cluster core and is the free-fall velocity of the parent cluster (gas reservoir). Thus, whereas collisions are very unlikely in a relatively low-mass, low-internal-velocity system such as the Orion Nebula Cluster, they become considerably more important at the mass and velocity scales characteristic of globular clusters. Thus, stellar collisions in response to accretion-induced core shrinkage remain a viable prospect in more massive clusters, and may contribute to the production of intermediate-mass black holes in these systems.

Keywords: celestial mechanics; stars: formation; galaxies: star clusters

Journal Article.  3528 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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