The evolution of dwarf galaxies: A comparison of UBVR photometry

Abstract

The proposed evolutionary link between dwarf irregular and dwarf elliptical/spheroidal galaxies is investigated using broad-band UBVR photometry obtained for a sample of 29 dwarf galaxies. The galaxies span a range of absolute B-band magnitude from -13.67 to -19.86 mag, and range in distance from about 7 to 108 Mpc. Broad-band colours and Sérsic surface brightness profile fits are compared for the two morphological types. All optical parameters are statistically different between the two subsamples, as evidenced by the significance level of the Kolmogorov-Smirnov statistic. Others have noted that dwarf ellipticals might have looked much like the currently observed dwarf irregulars in the past based on optical colours. A difference is noted between the two samples in the value of n (the power-law exponent determined from the Sérsic profile fitting), suggesting that the two main types of dwarf galaxy are structurally distinct. The differences in the structure of the stellar components imply that dwarf irregulars do not evolve to become dwarf ellipticals in isolation, meaning that some sort of external interaction is required if the transformation is to occur. The environments of the galaxies are initially classified as either field or group/cluster (though no definitive environmental comparison is presented here). © 2010 The Author. Journal compilation © 2010 RAS.