Gas and stars in spiral galaxies are modelled with the DUAL code, using
hydrodynamic and N-body techniques. The simulations reveal morphological
differences mirroring the dual morphologies seen in B and K' band observations
of many spiral galaxies. In particular, the gaseous images are more flocculent
with lower pitch angles than the stellar images, and the stellar arm-interarm
contrast correlates with the degree of morphological decoupling.Comment: 4 pages, 4 figures, to appear in Disk of Galaxies: Kinematics,
Dynamics and Perturbations, ASP Conf. Series, 200