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Are the most metal-poor galaxies young?

Published online by Cambridge University Press:  01 August 2006

Daniel Kunth  and
Göran Östlin
Daniel Kunth
Affiliation:
Institut d'Astrophysique de Paris, 98bis Boulevard Arago, F75014 Paris, France email: [email protected]
Göran Östlin
Affiliation:
Stockholm observatory, AlbaNova University Center, 10691 Stockholm, Sweden email: [email protected]
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Abstract

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We review the possibility that metallicity could provide a diagnostic for the age of a galaxy, hence that the most metal-poor star forming galaxies in the local universe may be genuinely young. Indeed, observational evidence for “downsizing” shows the average age of the stars in a galaxy to decrease with decreasing mass and metallicity. However, we conclude both from observational and theoretical viewpoints that metallicity is not an arrow of time. Consequently the most metal–poor galaxies of our local universe are not necessarely young. Current observations suggest that an old stellar population is present in all metal-poor galaxies, although a couple of cases, e.g. IZw18, remain under debate. Further observations with more sentitive equipement should settle this question in the coming years.

Keywords

galaxies: abundancesdwarfevolution
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 2 , Symposium S235: Galaxy Evolution Across the Hubble Time , August 2006 , pp. 61 - 64
Copyright
Copyright © International Astronomical Union 2007

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