  We investigate the star formation activity in galaxy pairs in chemical
hydrodynamical simulations consistent with a Lambda-CDM scenario. A statistical
analysis of the effects of galaxy interactions on the star formation activity
as a function of orbital parameters shows that close encounters (r < 30 kpc/h)
can be effectively correlated with an enhancement of star formation activity
with respect to galaxies without a close companion. Our results suggest that
the stability properties of systems are also relevant in this process. We found
that the passive star forming galaxies pairs tend to have deeper potential
wells, older stellar populations, and less leftover gas than active star
forming ones. In order to assess the effects that projection and interlopers
could introduce in observational samples, we have also constructed and analysed
projected simulated catalogs of galaxy pairs. In good agreement with
observations, our results show a threshold (rp < 25 kpc/h) for interactions to
enhance the star formation activity with respect to galaxies without a close
companion. Finally, analysing the environmental effect, we detect the expected
SFR-local density relation for both pairs and isolated galaxy samples, although
the density dependence is stronger for galaxies in pairs suggesting a relevant
role for interactions in driving this relation.
