The distribution of satellite galaxies

We carry out a statistical analysis of the distribution of faint satellites around galaxies of differing Hubble type. Following Holmberg, we count the number of faint images on Schmidt survey plates around primaries of known redshift. Our procedure leads to a highly significant detection of the satellites. On average, the projected distance of these systems from their primaries is distributed as Σ (r_p) ∝r^-γ_p with γ~0.9. The satellite populations around primaries of different Hubble type are significantly different: satellites are more concentrated around early-type primaries, with a higher absolute abundance within ∼0.25h^-1 Mpc.¹ If we assume a standard 'field' luminosity function, we find that galaxies with -18<5<-17² are about three times more weakly clustered to their primaries than are bright galaxies at separations of order 1 Mpc. At fainter magnitudes, the clustering appears stronger, suggesting the presence of a new population of dwarfs which exist only in close association with bright galaxies.