In a typical spiral galaxy, a disk shows details whose origin and dynamics are not yet well-understood. These include, a thin disk and a thick disk component with vastly different kinematical properties; an extended radial structure with a fall-off at large radii that is not well-understood; misalignment in the outer parts as resulting in a warp; non-axisymmetric features like bars and spiral arms that are expected to lead to radial migration.

Understanding the role secular evolution processes and environmental effects have in shaping galaxy disks requires to look for and to quantify the characteristics of all these different components - their sizes, dependence, if any, on the galaxy Hubble type and on the environment, their evolution with look-back time, .. - and compare them with the predictions of numerical simulations and analytical models.

This one-day special session aims to bring together observers, modelers and theoreticians to make the point on the study of the structure of galaxy disks: which are the main characteristics observed in their stellar and gaseous components? How do they depend on the Hubble type or on the environment? Which observed features can be more fruitfully compared to models in order to constrain the formation mechanisms?

SOC: Paola Di Matteo, Chanda Jog