PI: Simon Ellis, AAO, firstname.lastname@example.org
Address: AAO, PO Box 296, Epping, NSW 2122, Australia
CoI: Roberto de Propris, Univ. of Bristol
CoI: Joss Bland-Hawthorn, AAO
Title: Galaxy downsizing as a function of environment
Abstract: Galaxy downsizing is the phenomenon whereby less massive galaxies are observed to undergo star-formation at later epochs than massive galaxies. This anti-hierarchical behaviour may reperesent a serious problem for current models of galaxy formation. Galaxy downsizing manifests itself as a truncation of the colour-magnitude relation, beyond which fainter galaxies have colours bluer than the usual red- sequence of early-type cluster galaxies. If downsizing can be reconciled with hierarchical structure formation then there will exist a relation between the truncation magnitude of the colour-magnitude relation and the mass of the cluster. We will measure this directly via deep SQIID imaging of X-ray clusters at 0.5 \le z \le 0.61, and determine the star-formation history of galaxy clusters as function of galaxy mass and environment.
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