Morphology and kinematics of the interacting elliptical galaxies NGC 750 and NGC 751 = ARP 166. Velocity fields of tidally distorted elliptical galaxies.

New morphological and kinematical data of the elliptical galaxies NGC 750 and 751 (Arp 166) show that they are in the process of efficient tidal interaction. The galaxy centres are separated by 21 arcsec (or 10 kpc in projection). The isophotes show drastic deviations from the elliptical shape at all radii. Pointed and drop-shaped near- central isophotes suggest that the time-varying potential of the two galaxies is evolving slowly. Moreover, both luminosity profiles show significant deviations from the r^1/4^-law at all radii. Long-slit spectroscopy for five slit positions reveals peculiar kinematical properties of the two galaxies, which have almost identical central radial velocities. While NGC 750 exhibits nearly flat radial velocity curves, the radial velocity curves of NGC 751 are characterized by large variations of more than 100 km s^-1^ along the slit for all slit positions, probably reflecting initial regular rotation of NGC 751 which was disturbed in the course of the encounter. Both galaxies exhibit asymmetric and in part by large amounts radially increasing velocity dispersion curves. An encounter scenario is proposed in which the three-dimensional relative velocity of the two galaxies is very low, so that tidal coupling of a large fraction of stellar orbits is the dominant tidal effect. If this scenario applies, the galaxies rapidly will merge.