Unveiling the nature of the low surface brightness stellar host in blue compact dwarf galaxies

In order to characterize the low surface brightness component in blue compact dwarf galaxies, we determine their structural parameters for eight objects by fitting a Sersic law to their B, V, and R light profiles. We restrict the fit to the outer regions, excluding the starburst emission with the help of color and H alpha maps. We discuss the problems and the uncertainties involved in fitting the Sersic model, in particular the limited surface brightness interval and the sky-subtraction errors. We show that by carefully selecting the fitted radial range and by performing consistency checks on the fits in the different bands we can derive reliable structural parameters. All galaxies but one show very good agreement on the Sersic parameters in the three bands. Six of these galaxies have Sersic indexes n very close to 1, while the other two have n similar to 2.5. We compare the distribution of the BCDs with that of dI, dE, and LSB galaxies in the diagrams built upon the Sersic parameters. While previous works claimed that BCDs are segregated from the other dwarfs in such diagrams, here we find that six BCDs occupy the same region as the other dwarf types, while two galaxies have larger n, smaller Re, and brighter mu(0). These results indicate that evolutionary connections between BCDs and the other dwarf classes cannot be ruled out.