Stellar populations in globular cluster cores: evidence for a peculiar trend among red giant branch stars

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 3σ confidence level, whereas the relation is linear to within one standard deviation for main-sequence turn-off (MSTO) 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 MSTO 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.