We used an N-body smoothed particle hydrodynamics algorithm , with a detailed treatment of star formation , supernovae feedback , and chemical enrichment , to perform eight simulations of mergers between gas-rich disc galaxies .
We vary the mass ratio of the progenitors , their rotation axes , and their orbital parameters and analyze the kinematic , structural , and chemical properties of the remnants .
Six of these simulations result in the formation of a merger remnant with a disc morphology as a result of the large gas-fraction of the remnants .
We show that stars formed during the merger ( a sudden starburst occur in our simulation and last for 0.2 - 0.3 { Gyr } ) and those formed after the merger have different kinematical and chemical properties .
The first ones are located in thick disc or the halo .
They are partially supported by velocity dispersion and have high [ \alpha / Fe ] ratios even at metallicities as high as [ Fe / H ] = -0.5 .
The former ones – the young component – are located in a thin disc rotationally supported and have lower [ \alpha / Fe ] ratios .
The difference in the rotational support of both components results in the rotation of the thick disc lagging that of the thin disc by as much as a factor of two , as recently observed .
We find that , while the kinematic and structural properties of the merger remnant depends strongly upon the orbital parameters of the mergers , there is a remarkable uniformity in the chemical properties of the mergers .
This suggests that general conclusions about the chemical signature of gas-rich mergers can be drawn .