Structure and stellar content of dwarf galaxies. VI. B, V and R photometry of northern field dwarf galaxies

CCD photometry in the Cousins B, V and R bands of 19 northern field dwarf galaxies is presented. For each galaxy, and for each colour, we determined total magnitude, effective radius and effective surface brightness, and, by fitting an exponential to the surface brightness profile, central surface brightness and exponential scale length. Surface brightness and colour profiles are shown. One of the observed galaxies (UGC 2689) is probably a background S0 galaxy and belongs to the cluster Abell 426. All others, with one possible exception (Kar 49), are typical late-type field dwarf galaxies (mostly magellanic irregulars) lying in the distance range 5-10 Mpc. The sample has a median absolute magnitude M_B = -14.9 and a median colour (B-V) = 0.52. The present late-type dwarfs have higher surface brightness in the mean than cluster late-type dwarfs, confirming a trend found in our previous work. However, there is no evidence for a photometric difference between field and group late-type dwarfs. This paper is part of a long-term programme to study the environmental differences in the photometric structure of dwarf galaxies. Based on observations made at Observatoire de Haute Provence (CNRS), France.