Maximum stellar mass versus cluster membership number revisited

TL;DR

This study compiles and analyzes data on maximum stellar mass versus cluster size to test if observations align with random sampling predictions, finding no strong deviation from the hypothesis.

Contribution

It provides a new compilation of observational data and discusses how selection methods influence the observed distribution, challenging previous claims of deviation from random sampling.

Findings

Data does not show significant deviation from random drawing expectations.

Selection biases affect the observed distribution of maximum stellar mass.

No strong evidence for a lower maximum stellar mass in low-mass clusters.

Abstract

We have made a new compilation of observations of maximum stellar mass versus cluster membership number from the literature, which we analyse for consistency with the predictions of a simple random drawing hypothesis for stellar mass selection in clusters. Previously, Weidner and Kroupa have suggested that the maximum stellar mass is lower, in low mass clusters, than would be expected on the basis of random drawing, and have pointed out that this could have important implications for steepening the integrated initial mass function of the Galaxy (the IGIMF) at high masses. Our compilation demonstrates how the observed distribution in the plane of maximum stellar mass versus membership number is affected by the method of target selection; in particular, rather low n clusters with large maximum stellar masses are abundant in observational datasets that specifically seek clusters in the environs of high mass stars. Although we do not consider our compilation to be either complete or unbiased, we discuss the method by which such data should be statistically analysed. Our very provisional conclusion is that the data is not indicating any striking deviation from the expectations of random drawing.