We adopt a scenario in which the Galactic thick disk was formed by minor merging between the first generation of the Galactic thin disk ( FGTD ) and a dwarf galaxy about \sim 9 Gyr ago and thereby investigate chemical and dynamical properties of the Galactic thick disk .
In this scenario , the dynamical properties of the thick disk have long been influenced both by the mass growth of the second generation of the Galactic thin disk ( i.e. , the present thin disk ) and by its non-axisymmetric structures .
On the other hand , the early star formation history and chemical evolution of the thin disk was influenced by the remaining gas of the thick disk .
Based on N-body simulations and chemical evolution models , we investigate the radial metallicity gradient , structural and kinematical properties , and detailed chemical abundance patterns of the thick disk .
Our numerical simulations show that the ancient minor merger event can significantly flatten the original radial metallicity gradient of the FGTD , in particular , in the outer part , and also can be responsible for migration of inner metal-rich stars into the outer part ( R > 10 kpc ) .
The simulations show that the central region of the thick disk can develop a bar due to dynamical effects of a separate bar in the thin disk .
Whether rotational velocities ( V _ { \phi } ) can correlate with metallicities ( [ Fe/H ] ) for the simulated thick disks depends on the initial metallicity gradients of the FGTDs .
The simulated orbital eccentricity distributions in the thick disk for models with higher mass-ratios ( \sim 0.2 ) and lower orbital eccentricities ( \sim 0.5 ) of minor mergers are in good agreement with the corresponding observations .
The simulated V _ { \phi } - |z| relation of the thick disk in models with low orbital inclination angles of mergers are also in good agreement with the latest observational results .
The vertical metallicity gradient of the simulated thick disk is rather flat or very weakly negative at the solar neighborhood .
Our Galactic chemical evolution models show that if we choose two distinctive timescales for star formation in the thin and thick disks , then the models can explain both the observed metallicity distribution functions ( MDFs ) and correlations between [ Mg/Fe ] and [ Fe/H ] for the two disks in a self-consistent manner .
We discuss how the early star formation history and chemical evolution of the Galactic thin disk can be influenced by the pre-existing thick disk .