IC 5181: An S0 Galaxy with Ionized Gas on Polar Orbits

Abstract

The nearby S0 galaxy IC 5181 is studied to address the origin of the ionized gas component that orbits the galaxy on polar orbit. We perform detailed photometric and spectroscopic observations measuring the surface brightness distribution of the stars (I-band), ionized gas of IC 5181 (H-alpha narrow band), the ionized-gas and stellar kinematics along both the major and minor axis, and the corresponding line strengths of the Lick indices. We conclude that the galaxy hosts a geometrically and kinematically decoupled component of ionized gas. It is elongated along the galaxy minor axis and in orthogonal rotation with respect to the galaxy disk. The result is suggesting that the gas component is not related to the stars having an external origin. The gas was accreted by IC 5181 on polar orbits from the surrounding environment.