STELLAR DYNAMICS IN E+E PAIRS OF GALAXIES .2. SIMULATIONS AND INTERPRETATION

We have presented in a companion article a kinematic study of three EE galaxy pairs, NGC 741/742, 1587/1588 (CPG 99) and 2672/2673 (CPG 175 ). We find some evidence for perturbed velocity and velocity dispersio n profiles. These perturbation features are now reported for 14 galaxi es in the literature. They occur, or require observations for detectio n, at large radii where the S/N in the data is low. While observations of individual galaxies are sometimes uncertain, the large number of o bjects where such features are suspected gives confidence that they ar e real. These perturbations can be attributed to projection effects, c ontamination along the line of sight, or directly to the tidal interac tion. We report the results of several self-gravitating simulations of unbound pairs in an effort to better understand these perturbations a nd other generic features of close E+E pairs reported in the literatur e. The models frequently show off-center envelopes created by the asym metry of tidal forces during interpenetrating encounters. The envelope s last for a few 10(8) yrs, which explains the frequency of such featu res in observed pairs. This phenomenon is stronger in the self-gravita ting 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 t o be a robust indicator of the ongoing interaction. All simulations sh ow evidence for enhanced velocity dispersion between the galaxies even in the case of simple superposition of two non interacting objects. W e therefore conclude that this cannot be considered an unambiguous ind icator of the interaction.