Galactic Rings is a major review article that I wrote
in 1996 with Dr. Francoise Combes of the Paris Observatory.
The review was written at a time when it was thought that
galaxy rings in general are dynamical resonance features
driven by bar perturbations in galactic disks.
Other ideas have been proposed since that time that do
not necessarily involve orbit resonances. The review
can be accessed at the weblink at right.
Schematics of "OLR subclasses" of outer pseudorings in
barred galaxies. OLR stands for "outer Lindblad
resonance," one of the major low order disk resonances expected in a
The four galaxies shown here (clockwise from top left: NGC 2665,
UGC 12646, ESO 325-28, and ESO 577-3) show spiral patterns
whose characteristics are thought to be shaped by stellar orbit
families associated with the OLR. The schematic above is
based on two of these galaxies, and two others.
"Galactic Rings," by Ronald J. Buta and Francoise Combes, Fundamentals of Cosmic Physics,
17, 95, 1996
Recent Results on Ringed Galaxies