On the onset of runaway stellar collisions in dense star clusters I. Dynamics of the first collision

Understand

We study the circumstances under which first collisions occur in young and dense star clusters.

• The initial conditions for our direct $N$-body simulations are chosen such that the clusters experience core collapse within a few million years, before the most massive stars have left the main-sequence.
• It turns out that the first collision is typically driven by the most massive stars in the cluster.
• Upon arrival in the cluster core, by dynamical friction, massive stars tend to form binaries.