[TT2009] 52 , the SIMBAD biblio

We present a compilation of galaxies in the NGC 1023 Group, an accumulation of late-type galaxies at a distance of 10 Mpc. Members at high and intermediate luminosities were identified from their spectroscopic velocities. Members at low luminosities were identified from their morphologies on wide-field CCD images. The faint-end slope is in the range -1.27 < α < -1.12. There is evidence for two dwarf galaxy populations: one in the halo of NGC 1023 that is dominated by dwarf elliptical galaxies, and one in the infall region surrounding NGC 1023 that contains mainly dwarf irregular galaxies. Similar distinctive populations are observed in the Local Group.

Through our imaging surveys, a picture has emerged of the distributions and types of dwarf galaxies over a wide range of environments. Of greatest interest is a correlation between dwarf galaxy population and parent halo mass. The number of dwarfs per unit mass is constant over the range of halo masses 10¹²-10¹⁴M_☉. There are small but significant variations in luminosity functions with location. These variations can be attributed to differences in the bright and intermediate luminosity populations. In less evolved regions marked by substantial populations of spirals, galaxies with intermediate luminosity are relatively common, and such regions have low mass-to-light ratios. In more evolved regions where spirals are absent, there is relative depletion at intermediate luminosities and, overall in such places, mass-to-light ratios are high. Statistics are still poor for regions outside of massive haloes but the faint-end slope of the luminosity function is comparable in the field with what is found in the massive haloes. Everywhere that has been studied, the faint-end slope is unequivocally shallower than the slope at low masses anticipated by hierarchical clustering theory. Though the slope is shallow, there is no hint of a cut-off down to an observational limit of M_R = -10.