Numerical simulations of interacting gas-rich barred galaxies

Using an N-body + SPH code, we have performed numerical simulations to inve stigate the dynamical effects of an interaction between an initially barred galaxy and a small spherical companion. In the models described here the s mall companion passes through the disc of the larger galaxy perpendicularly to its plane. The impact positions and times are varied with respect to th e evolutionary phase of the bar and disc. The interactions produce expandin g ring structures, offset bars, spokes and other asymmetries in the stars a nd gas. They also affect the strength and pattern speed of the bar.