OBSERVATIONAL DETERMINATION OF THE NATURE OF GALACTIC SPIRAL ARMS

A test for the determination of the nature of the generation of spiral arms in galaxies is proposed. It is based on recent results of modell ing and numerical experiments, which have revealed the generation of a nticyclonic vortices simultaneous with that of spiral density arms. St udies of the dependence of the shape of spiral arms on the nature of t he mechanism for their generation (gravitational or hydrodynamic) are currently lacking; as shown in this paper, the locations of vortices r elative to the spiral arms, together with the observed rotation curve, may serve as a promising test to address this question.