Abstract details

We present the first results of our program to derive the complete star-formation history of the Local Group dwarf galaxy Leo A. Our analysis uses CMDs, obtained using HST, that reach below the oldest main-sequence turnoff. Less than 25\% of the star formation in Leo A can have occurred before a lookback time of 8 Gyr (z$\approx$1). Cosmological models predict that all of the prompt star formation should have occurred prior to the epoch of reionization at z$\approx$10 (t$_{look}$ $\approx$ 13.2 Gyr). It is not yet clear if this is the case for Leo A owing to the degeneracies of metallicity and age and the uncertainty introduced by the different assumptions made in the construction of theoretical stellar models.