Star formation histories in local group dwarf galaxies

I review observations made with the Hubble Space Telescope which have improved our view of both recent (ages <= 1 Gyr) and ancient (ages >= 1 Gyr) star formation histories in dwarf galaxies. The method of reconstructing recent star formation histories has been well tested, and now the major challenge is to build a large database of suitable observations of nearby dwarf irregular galaxies. With the exception of the dSph companions of our Galaxy., questions concerning the ancient star formation histories of nearby galaxies are stymied by a lack of suitably deep imaging observations. The few observations which do exist provide tantalizing evidence of strong evolution in star formation rates. This evolution is likely due to environmental effects, and we may be seeing evidence of the effects of reionization on the star formation histories of dwarf galaxies. Due to its wide field of view and its excellent imaging resolution, the proposed model for SNAP could solve these problems. (c) 2005 Elsevier B.V. All rights reserved.