Possible orbits of a satellite galaxy for shell formation in galaxy merger events

We investigated formation of stellar shells in mergers between the host spiral galaxy and its satellite galaxy in different scenarios. Results of previous works showed that stellar shells are formed in very radial mergers. We run N-body simulations for 4 Gyrs, with an M31-like host galaxy and spherical satellite. The simulations start with zero radial velocity. We found that the initial tangential velocities of 50 km/s and higher, in these merger scenarios, define orbits where stellar shells are not prominent in comparison with almost radial mergers. With a deviation from a very radial orbit defined with zero initial velocity, it is possible to have stellar shells formed with initial velocity up to 50 km/s for initial distance of 150 kpc, then for distance of 200 kpc with velocity up to 25 km/s, and for 250 kpc initial distance, stellar shells are formed only in a radial merger, after 2.5 Gyrs from the beginning of the simulation. With initial velocities higher than 100 km/s, we do not have stellar shells formation in these scenarios.