The morphology of multiple-nucleus brightest cluster galaxies

The morphology of 16 multiple-nucleus brightest cluster galaxies has been analyzed by modeling CCD images of the systems as line-of-sight superpositions of normal "secondary" cluster galaxies seen against a brighter "primary" galaxy. Fifty percent of the systems show morphological disturbances not seen in isolated elliptical galaxies and are thus assumed to be galaxies in tidal contact. Interaction effects include asymmetrical isophote distortions of the components, truncated brightness profiles of the secondaries, distended brightness profiles in the inner regions (r <~ 20 kpc) of the primaries, and the presence of faint plumes that may be dynamical friction wakes. The remaining 50% of the systems are morphologically consistent with super- position of undisturbed galaxies; their components are assumed not to be in tidal contact. No dynamical differences between interacting and noninteracting systems are apparent - interaction effects are found between components with large velocity differences ({DELTA}V > 1000 km s^-1^), which will lead to tidal stripping of the secondaries involved, as well as those more compatible with merging of the secondaries with the primaries ({DELTA}V < 300 km s^-1^). The average integrated luminosity of secondaries projected within the metric radius (r = 10h^-1^kpc) is 0.79L^* ^ for the entire sample; of this total the estimated luminosity of secondaries now being cannibalized is 0.17L^*^ per primary. When averaged over all Abell clusters, this result leads to an estimated cannibalism rate of L_T_~2L^*^ per 5 x 10^9^ yr for the brightest cluster galaxy. This in turn implies a dynamical correction of {DELTA}q_0_~0.3 to q_0_ measured from metric luminosities of brightest cluster galaxies.