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Matteo Monelli |
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"The ACS LCID project: star
formation histories of isolated galaxies in the Local Group" |
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I will present the main results of the Local Cosmology from Isolated Dwarfs (LCID) project, aimed at deriving detailed star formation histories over the life time of a sample of six Local Group isolated dwarf, low metallicity, galaxies: two dIrr (IC1613 and Leo A), two transition dIrr/dSph (LGS3 and Phoenix) and the only two isolated dSph in the Local Group (Cetus and Tucana). To accomplish this goal we have collected, using the ACS on board the HST, color-magnitude diagrams reaching their oldest main sequence turnoff (V $\sim$ 28) with good photometric accuracy. Accurate star formation histories have been derived through comparison with synthetic color-magnitude diagrams, using the IAC-pop algorithm. All galaxies in our sample, except Leo A, show a substantial amount of old stellar population, even though the subsequent evolution is varied. We will discuss the implications of these star formation histories on current scenarios of dwarf galaxy formation and evolution. |