GLOBULAR-CLUSTER SYSTEMS ASSOCIATED WITH CD GALAXIES IN POOR CLUSTERS

We present an analysis of direct CCD images of the central cD galaxies of four poor clusters (Albert, White, & Morgan 1977; Morgan, Kayser, & White 1975) obtained at the prime focus of the Canada-France-Hawaii Telescope. A globular cluster system (GCS) is detected in only one of the galaxies: NGC 4073 (MKW 4); it has a specific frequency of S(N) congruent-to 4 +/- 4, a value typical for an '' average '' elliptical of no particular distinction (Harris 1991). In the other three clusters, upper limits of S(N) < 5-10 can be set on the specific frequency of any attendant GCS. These findings strongly suggest that mergers are not important in the generation of extremely populous GCSs, since the central galaxies in poor clusters presumably have more active merging histories than do their counterparts in richer surroundings. It is noted that MKW 4 has a moderate cooling flow, which may play some role in the formation of its GCS; the other poor clusters studied have neither the cooling flow nor the detected GCS. Finally, we note that the GCS associated with NGC 4073, the cD galaxy in MKW 4, is among the least centrally concentrated of any studied to date. This supports a suggestion by Harris (1991) that the degree of central concentration of a GCS is a function of the luminosity of the parent galaxy, with the most luminous galaxies having the most distended cluster systems.