Recognizing merger remnants among normal elliptical galaxies: NGC 5813

It is suggested that departures from isothermal structure in the core brightness profiles of elliptical galaxies can be a signature of formation by mergers, since the more robust cores of small ellipticals can be shown to survive a merger with a giant elliptical under conditions in which the initial core radii differ by a factor of at least 8-10. The resulting core-within-core structure's inner core is predicted to have the smaller size, higher central surface brightness, smaller velocity dispersion, more rapid rotation, and bluer color characteristics of its lower progenitor luminosity. The outer core departs from the parameter correlations for normal ellipticals in the sense that would be expected if it had acquired the orbital energy and angular momentum of the 'victim'. Nonisothermal cores can result from the mergers, or from such nuclear mass concentrations as black holes.