The Dwarf Galaxy Population in Nearby Groups: The Data

Abstract

We used V and I CCD photometry to search for low-surface brightness dwarf galaxies (LSBD) in the central ( 22.5 V mag/arcsec 2, h > 1.5 arcsec, and diameters larger than 1.2 h -1 kpc. Twenty of the eighty galaxies are extended LSB galaxies that were detected only on smoothed images, after masking all high surface brightness objects. The completeness in the detection is ~80% for galaxies with V < 250 h -1 kpc), in agreement with the values found for satellites dwarfs around isolated E/S0 galaxies and in X-ray groups. The LSBD galaxies in the Mv-mu0 plane does not show a clear correlation, suggesting that the correlation noted by other studies could be produced by selection effects. The LSBD dwarf galaxies follow a well defined color-magnitude relation, extending for more than ten magnitudes (from bright ellipticals to faint dwarfs). A similar well defined color-magnitude relation from giants to dwarfs is known to be valid for galaxy clusters but it is the first time that it is demonstrated in the sparse environments of groups. (Abridge)