Surface BR photometry of newly discovered dwarf elliptical galaxies in thenearby Sculptor and Centaurus A groups

Prompted by the recent finding of a large number of gas-rich dwarf irregula r galaxies in the nearby southern galaxy groups Sculptor (Scl) and Centauru s A (Cen A) we carried out a complementary survey to search for members of the gas-poor dwarf elliptical (dE) galaxy family. In total 18 dE candidates were identified on SRC Sky Survey films covering the group regions. For fi ve dE's in the Sd, group and five in the Cen A group, membership informatio n is available from surface brightness fluctuations distance measurements; two dEs in each group also have independent redshift measurements. The rema ining eight galaxies have been associated to the groups based on their morp hology. We acquired deep B- and R-band CCD images for all galaxies and dete rmined their photometric and structural parameters. According to the magnit ude range covered, - 14 < M-B < - 9 (not counting the bright dS0 NGC 59), t hese objects are local dwarf spheroidal (dSph) analogues. The surface brigh tness profiles of most dwarfs are strongly nonexponential but are perfectly explained by the three-parametric Sersic law. The best-fitting Sersic para meters are compared with corresponding data for Virgo dE's and dSph's. The present dEs follow the relations between the Sersic parameters and absolute B-band magnitude for Virgo dE's and local dwarfs, thus confirming the memb ership in the Sd and Cen A groups, respectively. Most of our dwarfs exhibit color gradients in (B-R)(0), in the sense of a reddening outward. We also show and discuss the sky distributions and B-band luminosity functions of t he Sd and Cen A groups. The completeness magnitude for both populations (fr om the present survey) is estimated to be M-B(lim) approximate to - 13. We find that the composite luminosity function of four nearby galaxy groups is well fitted by a Schechter function down to M-B(lim) = -14 with a faint en d slope alpha = - 1.29(+/- 0.10). In the appendices we present best-fitting Sersic profile parameters for the dSph members of the Local Group and intr oduce two new dwarf irregulars found in the Cen A group.