Monday, August 14, 2006

E. Skillman on "Age-metallicity relations in Dwarfs"

How does the metallicity of stars in dwarf galaxies behave with their age? Simply measuring the age and the metallicity does sound straight forward, but is difficult to carry out. It is expected that stars produce metals and enrich the galaxy in metals, but does the expected enrichment from our knowledge of stars match with the observed values?

Calibrations from the LMC (Cole et al. 2005) show a quick increase in Fe/H in the beginning, but not big evolution during the last 5 Gyr. This of course depends on the star formation history and in the dwarf-spheroidal galaxy Leo I (or was it II?) which shows significant recent SF, the metallicity only went up after this. Enrichment that follows star formation is also found in local group dwarf-irregular galaxies.

Talking about the gas content is difficult, since the history of gas infall is not determinable, except by assuming that gas infall is correlated with the star formation rate.

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