The galactic structure towards the Galactic Centre .3. A study of Baade's window: Discovery of the bar population?

The analysis is presented of CMDs from Baade's Window. We decompose in a statistical sense the contributions from a mix of stellar populations. A non negligible contribution from a hitherto unaccounted stellar population is identified between V = 15(m).0-17(m).5 with a V-I colour ranging from 1(m).7 to 3(m).0. The star counts in 0(m).20 colour slices indicate that this contribution should have a spheroidal distribution with possibly some flattening: a triaxial Bar? Introduction of the bar population (8-9 Gyr and Z=0.005-0.030) gives a better agreement. The differences between the various fields are most likely related with the structure and the inclination angle of the Bar in the disc. Further indications are found that in the central regions, where the density increases, a significant drop in the disc density, described with an exponential, is present. With the scale heights from the various disc populations the distribution of the galactic open clusters perpendicular to the Galactic Plane can be explained. From this comparison indications are found that the scale height is a function of the age. The radial distribution of these clusters indicates that the disc scale length is probably increasing with the age. In first approximation a linear relation yields: h(0)(t(9)) = 2.3 + 0. 12t(9) kpc, where t(9) is given in Gyr.