Deviations from the universal Initial Mass Function in binary star clusters

TL;DR

This study uses N-body simulations to show that deviations from the standard IMF in binary star clusters can result from dynamical evolution, not necessarily different star formation physics.

Contribution

It demonstrates that observed IMF deviations in binary clusters may be due to dynamical effects rather than different initial star formation conditions.

Findings

Binary clusters often show IMF deviations due to dynamical evolution.

Mass resolution limits influence the observed IMF deviations.

Dynamical processes can mimic signs of different star formation physics.

Abstract

The stellar mass distribution in star-forming regions, stellar clusters and associations, the Initial Mass Function (IMF), appears to be invariant across different star-forming environments, and is consistent with the IMF observed in the Galactic field. Deviations from the field, or standard, IMF, if genuine, would be considered strong evidence for a different set of physics at play during the formation of stars in the birth region in question. We analyse N-body simulations of the evolution of spatially and kinematically substructured star-forming regions to identify the formation of binary star clusters, where two (sub)clusters which form from the same Giant Molecular Cloud orbit a common centre of mass. We then compare the mass distributions of stars in each of the subclusters and compare them to the standard IMF, which we use to draw the stellar masses in the star-forming region from which the binary cluster(s) form. In each binary cluster that forms, the mass distributions of stars in one subcluster deviates from the standard IMF, and drastically so when we apply similar mass resolution limits as for the observed binary clusters. Therefore, if a binary subcluster is observed to have an unusual IMF, this may simply be the result of dynamical evolution, rather than different physical conditions for star formation in these systems.