| Abstract | We have carried out a survey of low-surface brightness dwarf galaxies of all varieties on 24 deep (2^h^-3^h^ exposure) IIIaJ Palomar Schmidt plates, covering two strips at declination zones +30^deg^ and +48^deg^, centered on R.A. ~12^h^. Based on morphological criteria, a total of 179 dwarfs and dwarf candidates have been located, about one third of which were known previously. A maximum depth of v ~4000 km s^-1^ was reached for systems of M_B_ -16. Positions, morphological types, total magnitudes, diameters, axis ratios, and velocities (where available) are given for all 179 objects. Comparing their distribution with the distribution of 156 bright Zwicky galaxies sampled in the same volume, the following qualitative results were found. Dwarf galaxies fall into the structures delineated by luminous galaxies; there is no evidence for segregation of bright and faint galaxies on large scales. This includes dwarf elliptical galaxies, which have not generally been considered in previous studies. However, there is strong morphological segregation among the dwarfs. Dwarf irregulars are more dispersed than dwarf ellipticals which are predominantly found in clusters and dense groups. Outside, the dwarf ellipticals tend to be close companions (satellites) to massive giants. Only one good candidate for a truly isolated dE has been found in the survey. The overall abundance of dwarf galaxies in the field (outside of clusters) is fixed by the faint-end slope of the luminosity function. Our deep dwarf counts are consistent with a flat faint end; this was conjectured before on the basis of bright field samples. The relative abundance of dwarf galaxies is hence much lower in the field than in clusters, where the faint end of the LF is steeply rising. The results are strongly opposing a certain class of "biased galaxy formation" models that predict dwarf galaxies to be more uniformly distributed than luminous galaxies. We also discuss possible implications for the origin of dwarf elliptical galaxies. |
