Stellar Populations in Globular Cluster Cores: Evidence for a Peculiar Trend Among Red Giant Branch Stars

TL;DR

This study examines how the number of red giant branch stars in globular cluster cores relates to core mass, revealing a surplus in less massive clusters possibly due to complex dynamics and stellar evolution effects.

Contribution

It provides new evidence of a peculiar trend in red giant branch stars in globular clusters, highlighting a surplus in low-mass cores and exploring underlying causes.

Findings

Red giant branch stars scale sub-linearly with core mass.

Main-sequence turn-off stars scale linearly with core mass.

Surplus of red giant branch stars in less massive cluster cores.

Abstract

We investigate the relationship between the mass of a globular cluster core and the sizes of its various stellar populations in a sample of 56 globular clusters. The number of core red giant branch stars is found to scale sub-linearly with core mass at the 3-$\sigma$ confidence level, whereas the relation is linear to within one standard deviation for main-sequence turn-off and sub-giant branch stars. We interpret our results as evidence for a surplus of red giant branch stars in the least massive cluster cores which is not seen for main-sequence turn-off and sub-giant branch stars. We explore various possibilities for the source of this discrepancy, discussing our results primarily in terms of the interplay between the cluster dynamics and stellar evolution.