Metallicity of F and G dwarfs and the star formation problem

With high statistical conficence, the metallicity functions for disk-population F and G dwarfs have a central dip (at [Fe/H]=-0.1). Both types of stars have nearly the same form of metallicity function, with cutoffs at [Fe/H]=-0.5 and +0.3, practically the same mean value and dispersion, and a central dip dividing the stars into two groups by metal abundance. Yet comparison of the kinematics for the two groups paradoxically reveals that metal-rich G dwarfs are kinematically older than F dwarfs whose metal abundance is almost twice as low. The implications of this result for the star formation problem are discussed. The paradox cannot be resolved by the evolution of old F dwarfs into red giants. Of special interest is the fact that the proportion of metal-poor stars is the same among F as among G dwarfs