The model of stellar population synthesis built by our team for two decades is used to elaborate a global view of the Galaxy including dynamical and evolutionary aspects. Scenarii for the formation and evolution produces theoretical distribution functions which are directly compared with survey observations of different types (photometry, kinematics, abundance distributions)

We link the kinematical and dynamical point of view to an evolution scheme through a key parameter : the stellar ages. The age distribution of stars in the solar neighbourhood is derived from a model of galactic evolution. The stellar populations of the galactic disc are selfconsistently constrained by the Boltzmann and Poisson equations through the potential of the mass model. Thus we directly derive observational predictions from an overall description of galactic structure and evolution.

A complete description of the model inputs can be found in Robin, Reylé, Derrière, Picaud (2003). It includes:

• 4 populations (thin disc, thick disc, spheroid, bulge)
• Each population is described by a SFR history, an IMF, an age or age-range, a set of  evolutionary tracks, kinematics, metallicity characteristics, and includes a white dwarf population
• Density laws for the thin disc are constrained self-consistently by the potential via the Boltzmann equation and are age dependent.
• The extinction is modeled by a diffuse thin disc. This is not reliable for the galactic plane where a more sophisticated 3D extinction model should be used instead. The user can include an extinction distribution along the line of sight of his own.

The model is a powerful tool to constrain either evolutionary scenarii or galactic structure hypothesis through the comparison between model predictions and a large variety of observational constraints such as star counts, photometry or astrometry.

Model simulations are produced in the form of

• catalogues of pseudo-stars, from Monte-Carlo simulations. For each stars, observable parameters as well as intrinsic ones are given.
• tables of statistical distributions as a function of either observables (magnitudes, colours, proper motions, radial velocities) or intrinsic parameters (distances, spectral type, age, absolute magnitude).
• Integrated luminosity in any specified photometric band among UBVRIJHKL. Other photometric systems are being studied

A number of quantitative results has been obtained by comparing model predictions with suitable observations, like multidirectional photometric and astrometric star counts. Most important ones concern:

• constraints on thin disc evolution and star formation history (Initial Mass Function, Star Formation Rate and age-velocity dispersion relation, Haywood, 1993, 1994, Haywood et al., 1995)

• the scale length and radial cutoff of the galactic thin disc (Robin et al., 1992a and b)

• the determination of the thick disc structural parameters, local density, metallicity and kinematics, which parameters favour a scenario of formation of the thick disc by a merging event at the beginning of life of the thin disc (Ojha,1994, Ojha et al., 1995, Robin et al., 1996)
• the thick disc IMF (Reylé, Robin, 2001, A&A  373, 886)
• the spheroid structural parameters, local density and IMF ( Robin, Reylé, Crézé, 2000, A&A 359, 103-112)
• the warp and flare parameters for the disc (Derrière & Robin, 2001, In "The new era of wide-field astronomy" ASP Conference series, vol. 232, A. Adamson R. Clowes et G. Bromage, editors, page 229, San Francisco, 2001)
• the bulge population (Picaud et al. in preparation)

The spurious structure close to the plane is due to the model of diffuse extinction which becomes unreliable at b<5 degree. It shows how the Galaxy would be seen if the extinction was homogeneous with a scale height of 140 pc.