| Abstract | Redshifts have been measured for 14 galaxies brighter than V = 16 in a 1.5 degree square field centered on the relatively isolated elliptical galaxy NGC 720. Six of these have redshifts within 600 km/s of that of NGC 720, well in excess of the number expected for a randomly chosen field. Within the field surveyed, they show a significant tendency to cluster around NGC 720. Their combined luminosity is only 20 percent that of the elliptical. Their average distance from NGC 720 is 23 arcmin, and their dispersion about its redshift is 353 km/s. The possibility that five of the six, with redshifts significantly less than that of NGC 720, form a foreground group is considered but is ultimately discounted. With a half-light radius for NGC 720 of 38 arcsec, and an internal velocity dispersion of 214 km/s, the mass computed for the galaxy alone is smaller than the mass computed from the dynamics of its companions by a factor of 44 (albeit with considerable uncertainty). |
