Does subcluster merging accelerate mass segregation in local clusters?

Abstract

The nearest site of massive star formation in Orion is dominated by the Trapezium subsystem, with its four OB stars and numerous companions. The question of how these stars came to be in such close proximity has implications for our understanding of massive star formation and early cluster evolution. A promising route towards rapid mass segregation was proposed by McMillan et al., who showed that the merger product of faster evolving subclusters can inherit their apparent dynamical age from their progenitors. In this paper, we briefly consider this process at a size and time-scale more suited for local and perhaps more typical star formation, with stellar numbers from hundreds to thousands. We find that for reasonable ages and cluster sizes, the merger of subclusters can indeed lead to compact configurations of the most massive stars, a signal seen both in nature and in large-scale hydrodynamic simulations of star formation from collapsing molecular clouds, and that subvirial initial conditions can make an unmerged cluster display a similar type of mass segregation. Additionally, we discuss a variation of the minimum spanning tree mass-segregation technique introduced by Allison et al. © 2009 RAS.