Spiral arm star formation in barred galaxies

The two-fold disc-wide symmetry of spiral arms is generally attributed to density waves. Densisty wave theory can also explain a modulation of the star formation pattern along the arms according to the radial relation of the site with respect to the density-wave resonances. The degree of two-fold symmetry is reduced by the presence of a bar component. This is attributed to the increased radial mixing as a result of the non-axisymmetric bar structure. In order to quantify the influence of the bar component we selected a sample of spirals with various bar strengths.