"Gas in Globular Clusters: A Possible Way to Make Multiple Populations"

Abstract:

The escape speeds of globular clusters are generally larger than the speeds of red-giant and asymptotic giant-branch winds whilst in open clusters the escape speeds are much lower. The gas from such winds is therefore likely to be retained in globular clusters. Here I will discuss the possible consequences of such retained gas. This gas is unlikely to form new stars directly, as the star formation process will be disrupted by close encounters with the stars which are already present. Rather, the gas will accrete onto these pre-existing stars. In this talk, I will focus on how accretion onto a subset of main-sequence stars could produce a population of polluted stars. This mechanism may therefore be the explanation for the multiple populations observed in almost all globular clusters.