Projected surface density distribution of the stellar (orange) and gas (blue) particles. Top: fly-by scenario. Middle: mixed merger scenario. Bottom: wet merger scenario. The left panels show the stellar snapshots at the beginning of the simulation. The middle and right panels display selected snapshots highlighting the special structures. The simulations are performed with a spatial resolution of ∼50 pc. We define the first pericentric passage of the two galaxies in the merger scenario as the zeropoint in time. In the fly-by scenario, the black arrow marks the trajectory of the massive galaxy.