1995A&A...297...37C

We have presented in a companion article a kinematic study of three E+E galaxy pairs, NGC 741/742, 1587/1588 (CPG 99) and 2672/2673 (CPG 175). We find some evidence for perturbed velocity and velocity dispersion profiles. These perturbation features are now reported for 14 galaxies in the literature. They occur, or require observations for detection, at large radii where the S/N in the data is low. While observations of individual galaxies are sometimes uncertain, the large number of objects where such features are suspected gives confidence that they are real. These perturbations can be attributed to projection effects, contamination along the line of sight, or directly to the tidal interaction. We report the results of several self-gravitating simulations of unbound pairs in an effort to better understand these perturbations and other generic features of close E+E pairs reported in the literature. The models frequently show off-center envelopes created by the asymmetry of tidal forces during interpenetrating encounters. The envelopes last for a few 10⁸yrs, which explains the frequency of such features in observed pairs. This phenomenon is stronger in the self-gravitating simulations than in the MTBA runs. U-shaped (and an equal number of inverse U-shaped) velocity profiles are seen in the simulations, a result of ablation in the outer envelopes. Simulations including inner galaxy rotation also preserve this feature, irrespective of the spin vector direction in each galaxy. U-shape velocity structure is found to be a robust indicator of the ongoing interaction. All simulations show evidence for enhanced velocity dispersion between the galaxies even in the case of simple superposition of two non interacting objects. We therefore conclude that this cannot be considered an unambiguous indicator of the interaction.