Morphology of interacting elliptical galaxy pairs

CCD-photometry of 20 elliptical galaxy pairs was obtained in order to study the effects of galaxy interactions. Deviations from undisturbed brightness profiles are interpreted in terms of ongoing tidal interaction. The deviations include asymmetrical isophotes, distortions of the outer isophotes, twisting of the major axes of the outer isophotes with respect to the line connecting both galaxy centers, nonconcentric isophotes and extended or truncated brightness profiles.In particular, nonconcentric isophotes represent strong evidence in favour of ongoing interaction since they are generally not detected in undisturbed elliptical galaxies. The displacement of the nuclei with respect to the underlying galaxy is most probably explained as the consequence of a velocity impulse due to the perturbing galaxy. Brightness profiles of the brighter components in galaxy pairs are generally extended in comparison with brightness profiles of isolated elliptical galaxies. Truncated brightness profiles prevalent in most of the smaller components of galaxy pairs are interpreted as consequence of a tidally limited galaxy radius imposed by the more massive component.