SIMBAD references

We discuss the existence and the physical properties of the galactic thick disk by performing a global analysis of the multivariate star count sample, including magnitude, colours and proper motions in a 5-dimensional space (V, B-V, U-B, µ_l, µ_b) of observables. By combining the photometry and kinematical information, a series of significant clusters is derived by cluster analysis. The real star distribution is compared with the predictions of some stellar population models in the observational space and the ability of models to represent the data is tested through the coincidence between real data and simulated data in all clusters. Multivariate discriminant analysis has also been applied to visualize the thick disk population, otherwise unseen. All our results, using a new magnitude-colour-proper motion survey, show that the three-component model involving a thick disk with a scale height of 1170pc and velocity dispersions of (80, 55, 50)km/s provides a reasonable fit to the observed sample. The possibility that thick disk stars belong to the high-velocity tail of the old disk or to the low-velocity tail of the halo stars is ruled out. The thick disk with a lower scale height of 500pc and small velocity dispersions of (60, 39,35)km/s cannot fit the data as well.