KPG 390: A pair of trailing spirals.

In this study we present scanning Fabry-Perot Ha observations of the isolated interacting galaxy pair NGC 5278/79. We derived velocity fields, various kinematic parameters and rotation curves for both galaxies. These kinematical results together with the fact that dust lanes have been detected in both galaxies, as well as the analysis of surface brightness profiles along the minor axis, allowed us to determine univocally that both components of the interacting pair are trailing spirals. We have also estimated the mass of NGC 5278 fitting its rotation curve with a disk-halo component. We have tested three different types of halo (pseudo-isothermal, Hernquist and Navarro Frenk White) and we have obtained that the rotation curve can be fitted either with a pseudo-isothermal, an Hernquist halo or a Navarro Frenk White halo component, although in the first case the amount of dark matter required is about ten times smaller than for the other two halo distributions.