Using modern published data on velocities and spectroscopic definitions of chemical elements in stellar objects of the Galaxy , we investigated the relationship of chemical composition with the kinematics of different populations .
The paper shows that the old stellar populations of the Galaxy , belonging ( by the kinematic criterion ) to the thick disk subsystem—globular clusters , field variables of the type RR Lyrae ( lyrids ) , as well as close F–G dwarfs and field giants , have different chemical composition .
In particular , the dwarfs and giants of the field are on average more metallic than the globular clusters and lyrids of the field .
Moreover , the relative abundances of \alpha -elements in the range [ Fe / H ] > -1.0 are the highest for globular clusters , and are the lowest for for field variables of the RR Lyrae type .
Based on the analysis of the nature of the dependences of [ \alpha /Fe ] on [ Fe/H ] for these objects it was suggested that the thick disk subsystem in the Galaxy is composite and at least three components exist independently within it .
The oldest one includes metal-rich globular clusters that formed from a single proto-galactic cloud shortly after the start of type Ia supernovae outbursts .
Then the subsystem of field stars of a thick disk was formed as a result of “ heating ” of stars of already formed thin disk of the Galaxy by a rather massive dwarf satellite galaxy that fell on it .
And finally , subsystems of field stars with the kinematics of not only a thick , but even a thin disk that fell on the Galaxy from this captured satellite galaxy .