The fate of cannibalized fundamental-plane elliptical galaxies

Evolution and disruption of galaxies orbiting in the gravitational field of a larger cluster galaxy are driven by three coupled mechanisms: (1) tidal heating due to its time-dependent motion in the primary; (2) mass loss due to the tidal strain field; and (3) orbital decay. Previous work demonstrated that tidal heating is effective well inside the impulse approximation limit. Not only does the overall energy increase over previous predictions, but the work is done deep inside the secondary galaxy, e.g., at or inside the half-mass radius in most cases. Here these ideas applied to cannibalization of elliptical galaxies with fundamental-plane parameters. In summary, satellites with masses between 0.1% and 10% of a cluster giant are evaporated or significantly evolved by internal heating as they sink to the center. This suggests that long-lived merger-produced multiple nuclei giants should be rare. The precise location of the survival-evaporation boundary and the central concentration of the stripped-mass profile depend on the rate of orbital decay. Large secondaries evaporate preferentially, provided the orbital decay takes place over roughly five or more orbits. We estimate that secondaries with mass ratios as small as 1% on any initial orbit evaporate, and those on eccentric orbits with mass ratios as small as 0.1% evolve significantly and nearly evaporate in a galactic age. Captured satellites with mass ratios smaller than roughly 1% have insufficient time to decay to the center. After many accretion events, the model predicts that the merged system has a profile similar to that of the original primary with a weak increase in concentration.