Published in "Warped Disks and Inclined Rings Around Galaxies", 1991, eds. S. Casertano, P. D. Sackett, F. H. Briggs, Cambridge University Press
Abstract. A recently published photographic atlas and catalog of polar-ring galaxies and related objects is described, and a statistical analysis of some properties of the galaxies are tabulated. Roughly 0.5% of all nearby S0 galaxies appear to have polar rings. When corrected for various selection effects (e.g., non-optimal viewing orientation, possible dimming or limited lifetime of the ring) the percentage increases to about 5% of all S0 galaxies which now have, or have had in the past, a polar ring bright enough to make it into the catalog. The angle between the major axis of the two components shows a strong preference for being nearly perpendicular. However, deviations of 10-30° degrees are not uncommon. Polar rings show a variety of shapes; roughly half are narrow like a wedding ring while the other half are extended annuli with the central region cut out. Roughly two-thirds of the rings show some obvious warping; of these, roughly half have an integral sign type warp, which is typical of most warped disk galaxies, while the other half show a peculiar banana-shaped warp. A fair correlation of the asymmetry of the ring with the presence of outer debris, and a weak correlation of the angle between the ring and disk with the ring asymmetry, offer the possibility of determining the approximate age of a polar-ring galaxy based on its morphological appearance.
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