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Australian Human Resources Institute Diversity Awards 2013 Finalist

Ben MacLean (Monash)

"Open Cluster Formation Clues from Chemical Abundances"

Abstract. Globular clusters, once thought to be examples of simple stellar populations, are now known to present significant chemical abundance patterns within isolated populations. These patterns include variations in helium abundances and the anticorrelations of O to Na and Mg to Al, of which the Na-O is seen in all globular clusters.The currently accepted theory is that these patterns are a result of self-pollution from intermediate-mass AGB stars undergoing ‘hot-bottom burning’ and the existence of multiple populations within globular clusters.Presented is a study on the abundances of stars in open clusters within the disk of the Milky Way, in order to search for evidence of multiple populations.Data on the O, Na, Mg, Al, Ba and Eu abundances in open cluster stars were gathered from sources throughout the literature and plotted along with a globular cluster template, galactic field stars and a galactic chemical evolution model for comparison. No evidence was found to support th e existence of multiple populations in any of the 20 open clusters analysed, with little separating the open clusters from the field. However,they were found to be more O-poor and Na-rich than the field, with evidence that many are chemically inhomogeneous in both O and Na, providing evidence for hot-bottom burning operating within open clusters in a similar way as it is thought to in globular clusters.

Held in the AAO Meeting Room (Room 7, 1st Floor, Building 2) at 11:00 AM on Thursday, 28 November 2013