Model of stellar population synthesis of the Galaxy


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:

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

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:
The resulting model can be used for simulations of the galactic stellar populations in any directions in photometric bands UBVRIJHKL as well as radial velocity and proper motion distributions. It may help for preparing observations, for evaluating the galactic stellar contamination in extragalatic studies or in star cluster fields.

Simulations :

  • Image in 3 colours of the Galaxy as would be seen from the sun. Colours are given by the integrated flux in bands BVR
    BVR image of the simulated Galaxy

  • Image in 3 colours of the Galaxy as would be seen from the sun. Colours are given by the integrated flux in bands JHK.

    JHK image of the simulated Galaxy
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.