2005ApJ...624..693K

The central, or x₁, family of periodic orbits is the most important one in almost all two-dimensional numerical models of galactic bars in the literature. However, we present evidence that in two-dimensional models with sufficiently large bar axial ratios (a/c≳6), stable orbits having propeller shapes play the dominant role. In our models this propeller family is in fact a distant relative of the x₁family. There are also intermediate cases in which both families are important. The dominance of one family over the other may have direct consequences on the morphological properties of the bars that can be constructed from them, properties such as face-on bar thinness and strength as well as the boxiness of the outer isophotes.