We investigated star formation histories of 20 irregular galaxies through a newly developed method of analyzing area-integrated optical spectra. This method is complementary to other methods for investigating star formation history. We obtained an area-integrated spectrum of each galaxy from 3900 to 6900 Å with an accuracy of ∆ (B-V) ∼ 0.05 mag. The obtained spectrum is decomposed by a set of template spectra with different ages. The templates correspond to four ages and have a unique solution in the decomposition. They are generated from PEGASE code. The decomposition is carried out by a maximum likelihood calculation with the help of the MOPED technique.
8th Asian-Pacific Regional Meeting, Volume II
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