Context : Two main scenarios for the formation of the Galactic bulge are invoked , the first one through gravitational collapse or hierarchical merging of subclumps , the second through secular evolution of the Galactic disc .

Aims : We aim to constrain the formation of the Galactic bulge through studies of the correlation between kinematics and metallicities in Baade ’ s Window ( l = 1 \degr , b = -4 \degr ) and two other fields along the bulge minor axis ( l = 0 \degr , b = -6 \degr and b = -12 \degr ) .

Methods : We combine the radial velocity and the [ Fe/H ] measurements obtained with FLAMES/GIRAFFE at the VLT with a spectral resolution of R=20000 , plus for the Baade ’ s Window field the OGLE-II proper motions , and compare these with published N-body simulations of the Galactic bulge .

Results : We confirm the presence of two distinct populations in Baade ’ s Window found in Hill et al .
2010 : the metal-rich population presents bar-like kinematics while the metal-poor population shows kinematics corresponding to an old spheroid or a thick disc one .
In this context the metallicity gradient along the bulge minor axis observed by Zoccali et al .
( 2008 ) , visible also in the kinematics , can be related to a varying mix of these two populations as one moves away from the Galactic plane , alleviating the apparent contradiction between the kinematic evidence of a bar and the existence of a metallicity gradient .

Conclusions : We show evidences that the two main scenarios for the bulge formation co-exist within the Milky Way bulge .