We performed an uniform spectroscopic analysis of 1111 FGK dwarfs observed as part of the HARPS GTO planet search program .
We applied a purely chemical approach , based on [ \alpha /Fe ] ratio , to distinguish the various stellar components in the Galaxy .
Apart from the well known Galactic thick and thin disks , we separated an \alpha -enhanced stellar family at super-solar metallicities .
The metal-rich high- \alpha stars have orbits similar to the thin disk stars , but they are similar to thick disk stars in terms of age .
Our data indicate that the incidence of stars with planets are greater among the chemically separated “thick” disk stars with [ Fe/H ] \lesssim -0.3 dex than they are among “thin” disk stars in the same [ Fe/H ] interval .
Our results allow us to suppose that a certain chemical composition , and not the Galactic birth place of the stars , is the causative factor for that .