Giant Cyclones in Gaseous Discs of Spiral Galaxies
  We report detection of giant cyclonic vortices in the gaseous disc of the spiral galaxy NGC 3631 in the reference frame rotating with the spiral pattern. A presence of such structures was predicted by the authors for galaxies, where the radial gradient of the perturbed velocity exceeds that of the rotational velocity. This situation really takes place in NGC 3631. 
A. M. Fridman, O. V. Khoruzhii, E. V. Polyachenko, A. V. Zasov, O. K.   Sil'chenko, V. L. Afanas'ev, S. N. Dodonov, A. V. Mo...