On the evolution of intra-cluster gas within Galactic globular clusters

Abstract

It has been known since the 1950's that the observed gas content of Galactic globular clusters (GCs) is 2-3 orders of magnitude less than the mass lost by stars between Galactic disk crossings. In this work we address the question: What happens to this stellar gas? Using an Eulerian nested grid code, we present 3D simulations to determine how stellar wind material evolves within the GC environment. We expand upon work done in the 70's and move a single-mass King-model GC through the Galactic halo medium, stripping a 10^5 Msun GC of its intra-cluster medium but predicting a detectable medium for a 10^6 Msun cluster. We find from new multi-mass King model simulations, the first to incorporate empirical mass-loss formulae, that the single-mass King model underestimates the retention of intra-cluster gas in the cluster. Lastly, we present a simple discretised multi-mass GC model, which yields lower levels of intra-cluster medium compared to the continuous single- and multi-mass King models. Our results show that there is still an issue with the predicted intra-cluster gas content of massive GCs. We conclude that by modelling GC systems more accurately, in particular the stellar structure and description of mass loss, we will be able to work towards resolving this issue and begin to fill in some of the gaps in our understanding of the evolution of globular clusters.