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Symposium 241

Abstract details

Stellar populations beyond the Local Group: the SFH of gas-rich dwarf galaxies in Centaurus A
M. Grossi, M. J. Disney, B. J .Pritzl, P. M. Knezek, J. S. Gallagher, R. F. Minchin, K. C. Freeman

We have analysed the stellar population and the gas distribution of three unusual dwarf galaxies in the Centaurus A group discovered with the HIPASS survey. In the optical they look like low surface brightness dwarf spheroidals, yet they are more gas-rich than the typical dwarf irregular galaxies in the Local Group. They should be favoured hosts for starbursts, whereas they do not show signs of massive star formation (SF). Comparison of our HST/WFPC2 observations with synthetic colour magnitude diagrams (CMDs) indicates that in these systems SF has been sporadic and local, but it has proceeded for several Gyrs. One object (HIPASS J1321-31) has a peculiar bright red plume in its CMD, suggesting that a "miniburst" occurred 300 - 500 Myr ago, followed by a period of relative quiescence.

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