The external origin of the polar gaseous disk of the S0 galaxy IC 5181
  Galaxies accrete material from the environment through acquisition and
merging events. We study the nearby S0 galaxy IC 5181 to address the origin of
the ionized-gas component orbiting the galaxy on polar orbit ionized gas of IC
5181 from broad and narrow-band imaging. We measure the ionized-gas and stellar
kinematics and the line strengths of the Lick indices of the stellar component
along both the major and minor axis. The age, metallicity, and [alpha/Fe]
enhancement of the stellar populations are derived using single stellar
population models with variable element abundance ratios. The ionized-gas
metallicity is obtained from the equivalent width of the emission lines. IC
5181 is a morphologically undisturbed S0 galaxy with a classical bulge made by
old stars with super solar metallicity and overabundance. Stellar age and
metallicity decrease in the disk region. 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.
We interpret the kinematical decoupling as suggestive of a component of gas,
which is not related to the stars and having an external origin. It was
accreted by IC 5181 on polar orbits from the surrounding environment.
