Dynamical modelling of the counterrotating stellar components in the S0 galaxy NGC 1366

In this work we study the highly-inclined S0 galaxy NGC 1366 in the Fornax cluster, which is known to host a stellar component that is kinematically decoupled from the main body of the galaxy. According to a parametric spectroscopic decomposition of the spectrum obtained along the galaxy major axis, the counter-rotating stellar component is younger, has nearly the same metallicity, and has a lower alpha-element overabundance than the co-rotating component. We build a two-integrals exploratory dynamical models of NGC1366 using an original code dedicated to the solution of the Jeans equations for axisymmetric multicomponent systems, and allowing for an easy treatment of counter-rotation. The models include only a Sérsic bulge and a Freeman disk and use constant Satoh parameters. We consider a non-rotating galaxy model, a non-rotating bulge model, as well as the case of maximally, mildly, and moderately counter-rotating models. Our results show that each counter-rotating model only partially reproduces the observed kinematics. We expect to improve the modelling by adding a DM halo and considering a space-dependent Satoh parameter. NGC 1366 can serve as a case study to be applied to other counter-rotating galaxies for understanding their structure and constraining their formation mechanisms.