THE STELLAR POPULATION STUDY OP THE POLAR RINGS IN THE GALAXIES NGC 2685 AND NGC 4650A

摘要

Polar ring galaxies (PRGs) are dynamically peculiar systems with a ring or annulus of gas, stars and dust orbiting in a plane nearly perpendicular to the equatorial plane of the host galaxy (Withmore 1990). According to the most popular point of view, PRGs are the result of galaxy interaction, which ranges from simple gas accretion to a complete merger. Alternatively, polar rings can represent the delayed inflows of primordial gas. Therefore, the problem of PR's age is actual (Eskridge & Podge 1997; Gallagher et al 2002). Deep single-star photometry can directly identify stars in various evolutionary phases through their positions on CMD. This can cast light on the origin and evolution of PRGs.