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Context. Many disk galaxies host two extended stellar components that rotatein opposite directions. The analysis of the stellar populations of thecounter-rotating components provides constraints on the environmental andinternal processes that drive their formation.  Aims. The S0 NGC 1366 in the Fornax cluster is known to host a stellarcomponent that is kinematically decoupled from the main body of the galaxy.Here we successfully separated the two counter-rotating stellar components toindependently measure the kinematics and properties of their stellarpopulations.  Methods. We performed a spectroscopic decomposition of the spectrum obtainedalong the galaxy major axis and separated the relative contribution of the twocounter-rotating stellar components and of the ionized-gas component. Wemeasured the line-strength indices of the two counter-rotating stellarcomponents and modeled each of them with single stellar population models thataccount for the {\alpha}/Fe overabundance.  Results. We found that the counter-rotating stellar component is younger, hasnearly the same metallicity, and is less {\alpha}/Fe enhanced than thecorotating component. Unlike most of the counter-rotating galaxies, the ionizedgas detected in NGC 1366 is neither associated with the counter-rotatingstellar component nor with the main galaxy body. On the contrary, it has adisordered distribution and a disturbed kinematics with multiple velocitycomponents observed along the minor axis of the galaxy.  Conclusions. The different properties of the counter-rotating stellarcomponents and the kinematic peculiarities of the ionized gas suggest that NGC1366 is at an intermediate stage of the acquisition process, building thecounter-rotating components with some gas clouds still falling onto the galaxy.

Kinematic and stellar population properties of the counter-rotating components in the S0 galaxy NGC 1366