Kinematics and dynamics of the M 51-type galaxy pair NGC 3893/96 (KPG 302)

Aims. We study the kinematics and dynamics of the M 51-type interacting galaxy pair KPG 302 (NGC 3893/96). We analyze the perturbations induced by the encounter on each member of the pair, as well as the distribution of the dark matter (DM) halo of the main galaxy in order to explore possible differences between DM halos of "isolated" galaxies and those of galaxies belonging to a pair. Methods, The velocity field of each galaxy was obtained using scanning Fabry-Perot interferometry. A two-dimensional kinematic and dynamical analysis of each galaxy and the pair as a whole are done emphasizing the contribution of circular and non-circular velocities. Non-circular motions can be traced on the rotation curves of each galaxy allowing us to differentiate between motions associated to particular features and motions that reflect the global mass distribution of the galaxy. For the main galaxy of the pair, NGC 3893, optical kinematic information is complemented with HI observations from the literature to build a multi-wavelength rotation curve. We try to fit this curve with a mass-distribution model using different DM halos. Results. Non-circular motions are detected on the velocity fields of both galaxies. These motions can be associated to perturbations due to the encounter and, in the case of the main galaxy, to the presence of a structure such as spiral arms. The location of the corotation radius of this galaxy is also explored. We find that the multi-wavelength rotation curve of NGC 3893, "cleaned" from the effect of non-circular motions, cannot be fitted whether by a pseudo-isothermal or by a NFW DM halo.