Dynamics of binary black holes in low-mass young star clusters

Understand

Young star clusters are dynamically active stellar systems and are a common birthplace for massive stars.

• Low-mass star clusters ($\sim{}300-10^3$ M$_\odot$) are more numerous than massive systems and are characterized by a two-body relaxation time scale of a few Myr: the most massive stars sink to the cluster core and dynamically interact with each other even before they give birth to compact objects.
• Here, we explore the properties of black holes (BHs) and binary black holes (BBHs) formed in low-mass young star clusters, by means of a suite of $10^5$ direct $N$-body simulations with a high original binary fraction (100 % for stars with mass $>5$ M$_\odot$).
• Most BHs are ejected in the first $\sim{}20$ Myr by dynamical interactions.