|Speaker||Talk Date||Talk Series|
|Nate Bastian (Liverpool John Moores)||6 March 2014||Institute of Astronomy Colloquia|
Globular clusters (GCs) are traditionally thought of as the quintessential simple stellar populations (i.e., all stars have the same age and abundance), however, we now know that all GCs show abundance spreads in certain elements, and that their colour-magnitude diagrams are not well represented by a single isochrone. Various scenarios have been put forward to explain these anomalies, and most invoke multiple star formation events within the clusters. While
GCs were generally thought to only form in the special conditions present in the early universe, one of the most surprising discoveries of the Hubble Space Telescope has been that GCs are still forming in the local universe today. These young massive clusters (YMCs) can be used to place strong constraints on the formation of GCs, in particular they can be used to test theories for the origin of the "multiple populations" of stars observed in GCs. I will present
recent results on YMCs, paying particular attention to whether they have undergone multiple star formation events, predicted by most scenarios for the multiple populations in GCs. No YMCs found to date show evidence of multiple bursts or extended star formation histories, ruling out previously preferred models (i.e. the "AGB scenario"). I
will present a new scenario for the origin of the multiple populations within GCs that does not require multiple star formation episodes.