Formation and Fragmentation of Gaseous Spurs in Spiral Galaxies
We believe that intermediate-scale spur structures, seen most clearly in
the Whirpool galaxy M51, may arise from self-gravitating instabilities in
magnetized spiral arms; the increased shear in interarm regions leads
to the ``backswept'' morphology. The enhanced densities within spurs
makes possible smaller-scale fragmentation, which may produce bound clouds
of a few million solar masses.
The Whirpool Galaxy