Astrophysical Journal, 665: pp. L45-L48.Some young star clusters show a degree of mass segregation that is inconsistent
with the effects of standard two-body relaxation from an initially unsegregated
system without substructure, in virial equilibrium, and it is unclear whether cur-
rent cluster formation models can account for this degree of initial segregation
in clusters of significant mass. In this Letter we demonstrate that mergers of
small clumps that are either initially mass segregated, or in which mass segrega-
tion can be produced by two-body relaxation before they merge, generically lead
to larger systems which inherit the progenitor clumps’ segregation. We conclude
that clusters formed in this way are naturally mass segregated, accounting for the
anomalous observations and suggesting that this process of prompt mass segre-
gation due to initial clumping should be taken fully into account in constructing
cluster dynamical models
