7 Conclusions

We have carried out CCD photometry in the B, V, and R bands of 19 nearby field (non-group member) dwarf candidate galaxies as part of a long-term effort to establish a complete data base of photometric (structural) parameters for all dwarf galaxies lying within a distance of 10 Mpc. One of the selected candidates, UGC2689, upon closer inspection, turned out to be a likely background giant S0 galaxy. With one further exception, the possible dwarf elliptical Kar49, all imaged objects are typical late-type dwarf galaxies, mostly of the Im (magellanic) class, that dominate the galaxy population outside of clusters and rich groups of galaxies. Some of the dwarfs are obviously in a state of high star formation activity judged from their BCD morphology. Others are apparently faint because they are highly obscured by galactic dust extinction, being fairly luminous intrinsically (up to $M_B \approx -18$).

We provide surface brightness and colour profiles, global photometric parameters (total magnitudes, total colour indices, effective radii, effective surface brightnesses), as well as best-fitting exponential parameters (exponential scale lengths and central surface brightnesses) for all 19 galaxies.

The sample was not chosen to be homogeneous for a study in its own right, but simply to further enlarge the sample of nearby (closer than 10 Mpc) dwarf galaxies with known photometry, to be analysed comprehensively later on. Nonetheless, by comparing the photometric properties of our 17 field "irregulars'' with those of all late-type dwarfs determined in our previous work, and preliminarily analysed in Bremnes (2001), we find the same trend, namely that dwarf irregulars outside of clusters have higher surface brightness in the mean than cluster irregulars. However, there is no significant difference between the photometric properties of group members and true field dwarf irregulars. It seems that only a dense cluster environment can significantly alter the star formation history of an irregular.

To the 120 nearby (within 10 Mpc) dwarfs with known photometry we have added another ca. 20. There are still up to 100 nearby dwarf candidates, in both the southern and northern hemisphere, which remain to be imaged. In our future papers of this series we plan to provide the photometry of the remaining nearby dwarf objects and then, based on a more complete data base, carry out a final analysis of the systematic photometric properties of dwarf galaxies with respect to environmental differences.

Acknowledgements

F. D. B. and B. B. are grateful to the Swiss National Science Foundation for financial support. We thank the night assistants at OHP who supervised some of the observations in service observing. This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propultion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration, as well as NASA's Astrophysical Data System Abstract Service.