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Narrow Polar Rings versus Wide Polar Ring/Disk Galaxies

In the latest ten years, a big effort has given to study the morphology and kinematics of polar ring galaxies: many steps forward and new discoveries on the structure and formation mechanisms for such systems have been made during this time thanks to high resolution photometric and spectroscopic data. In this paper, I review the latest results obtained for this class of galaxies, from both observational and theoretical studies. I focus on the analysis of the observed properties (e.g., structure, colours, age, metallicity, and kinematics) for narrow and wide polar ring galaxies. In particular, I compare AM2020-504 and NGC4650A, which are the two prototypes for narrow and wide polar rings, respectively. I discuss similarities and differences between the two kinds of systems and how they reconcile with the main formation scenarios proposed for this class of galaxies.