THE SMALL-SCALE CLUSTERING PROPERTIES OF DWARF GALAXIES

We report two results on the small-scale clustering properties of dwarf galaxies identified in the vicinity of early-type Shapley-Ames galaxies on high-resolution photographic plates. 1. Dwarf galaxies display the same trend of stronger clustering toward earlier morphological type on small scales as their giant counterparts on larger scales. Early-type dwarfs have a surface density as a function of projected radial distance R from E-E/S0 galaxies of the form SIGMA(R) is-proportional-to R-1.22 +/- 0.05 for 25 < R < 400 kpc (H0 = 50) which mimicks that of the dark halos of spiral galaxies. It corresponds to a spatial two-point correlation function zeta(r) = (r/r0)-gamma with gamma = 2.22 and r0 = 10 Mpc. The steepness of gamma and the tendency of early-type dwarf galaxies to be satellites of giant galaxies suggest that early-type dwarf galaxies are the most strongly clustered of all galaxies. Our results indicate that early-type dwarfs can be used as dynamical probes of dark halos around early-type giant galaxies and as tracers of the dynamical evolution of such halos in dense environments. 2. The trend of increasing early-type dwarf frequency per early-type giant with environment richness previously established for rich groups is found to be continued in the less rich environments studied here. Our data cover a range in early-type dwarf to giant ratio of a factor of 20. We find a minimum value of approximately 0.25 for isolated early-type galaxies, as compared to a maximum of approximately 8 previously found in rich environments like the Virgo Cluster.