Abstract:
Non-barred ringed galaxies are among the ideal galaxies to study the role of both the internal dynamics of galaxies and the physics of accretion/interaction mechanisms. An especially interesting ring case is Hoag’s Object with its peculiar morphology: an elliptical-like core with a nearly perfect outer ring, and no signs of bar and stellar disc. Hoag-type galaxies, which bear strong resemblance to Hoag’s Object, are extremely rare and their origin is still debated. I will present our recent work that has revealed a unique case for Hoag-type galaxies: PGC 1000714 presents strong resemblance to Hoag’s Object, with an additional surprise — a second inner ring, which is older, more diffuse, and redder than the outer ring. This is a first description of a double ringed elliptical galaxy. Such peculiar systems help our understanding of galaxy formation in general, since they present extreme cases, providing clues on formation mechanisms.