Top: time of the merger as a function of the cutoff radius of the halo R_h, given in units of the scale radius of the disk R_d and assumed equal for the two galaxies. The initial tangential velocity here is fixed at 50 km s⁻¹. Bottom: correlation between the time of the merger and the initial tangential velocity in the case of no IGM. The cutoff radii of the halos here are fixed at 70 R_d.