A model of the tidal interaction between M 81 and NGC 3077

We have modelled the tidal interaction between M 81 and NGC 3077, and found that the spiral arms of M 81 and the bridge of H in between M 81 and NGC 3077 can be the results of a close encounter between the two galaxies. A good fit to observations is found with a model where NGC 3077 moves in an approximately parabolic prograde orbit in the plane of the disk of M 81. Since our model does not include M 82 or the other members of the M 81 group, it cannot give a complete description of the complex dynamics of, e.g., the intergalactic gas in the group.