Milky Way's Thick and Thin disk: Is there distinct thick disk?
  This article is based on our discussion session on Milky Way models at the
592 WE-Heraeus Seminar, Reconstructing the Milky Way's History: Spectroscopic
Surveys, Asteroseismology and Chemodynamical models. The discussion focused on
the following question: "Are there distinct thick and thin disks?". The answer
to this question depends on the definition one adopts for thin and thick disks.
The participants of this discussion converged to the idea that there are at
least two different types of disks in the Milky Way. However, there are still
important open questions on how to best define these two types of disks
(chemically, kinematically, geometrically or by age?). The question of what is
the origin of the distinct disks remains open. The future Galactic surveys
which are highlighted in this conference should help us answering these
questions. The almost one-hour debate involving researchers in the field
representing different modelling approaches (Galactic models such as TRILEGAL,
Besancon and Galaxia, chemical evolution models, extended distribution
functions method, chemodynamics in the cosmological context, and
self-consistent cosmological simulations) illustrated how important is to have
all these parallel approaches. All approaches have their advantages and
shortcomings (also discussed), and different approaches are useful to address
specific points that might help us answering the more general question above.
