Big Fish in Small Ponds: Massive Stars in the Low Mass Clusters of M83

TL;DR

This study uses Hubble data to examine the upper end of the stellar initial mass function in M83's clusters, finding it consistent with a universal IMF and revealing that small clusters can host massive stars without disrupting star formation.

Contribution

It demonstrates that the upper end of the IMF in M83 is consistent with universality and shows small clusters can contain massive stars regardless of cluster mass.

Findings

The upper end of the IMF in M83 aligns with a universal IMF.

Small clusters can host massive stars independent of their mass.

Massive stars in small clusters do not hinder star formation.

Abstract

We have used multi-wavelength Hubble Space Telescope WFC3 data of the starbursting spiral galaxy M83 in order to measure variations in the upper end of the stellar initial mass function (uIMF) using the production rate of ionizing photons in unresolved clusters with ages $\leq$ 8 Myr. As in earlier papers on M51 and NGC 4214, the upper end of the stellar IMF in M83 is consistent with an universal IMF, and stochastic sampling of the stellar populations in the $\lessapprox$ 10$^{3}$ Msun clusters are responsible for any deviations in this universality. The ensemble cluster population, as well as individual clusters, also imply that the most massive star in a cluster does not depend on the cluster mass. In fact, we have found that these small clusters seem to have an over-abundance of ionizing photons when compared to an expected universal or truncated IMF. This also suggests that the presence of massive stars in these clusters does not affect the star formation in a destructive way.