Stellar populations in the Galactic bulge
  AIMS:The aim of this paper is to study the characteristics of the stellar
populations and the metallicity distribution in the Galactic bulge. We study
the entire stellar population, but also retrieve information using only the red
clump stars. METHODS: To study the characteristics of the stellar populations
and the metallicity distribution in the Galactic bulge, we compared the output
of the galaxy model TRILEGAL, which implements the Binney et al. (1997) bulge
model, with observations from 2MASS and OGLE-II. A minimisation procedure has
been set up to retrieve the best fitting model with different stellar
populations and metallicity distributions. RESULTS: Using the TRILEGAL code we
find that the best model resembling the characteristics of the Galactic bulge
is a model with the distance to the Galactic centre $R_0 =
8.7\pm^{0.57}_{0.43}$ kpc, the major axis ratios of the bar $1:\eta:\zeta = 1 :
0.68\pm_{0.19}^{0.05} : 0.31\pm_{0.04}^{0.06}$, and the angle between the
Sun-centre line and the bar $\phi = 15\deg\pm_{12.7}^{13.3}$. Using these
parameters the best model is found for a burst of 8 Gyr, although it is almost
indistinguishable from models with ages of 9 and 10 Gyr. The metallicity
distribution found is consistent with metallicity distributions in the
literature based on spectroscopic results.
