Star formation rates and mass distributions in interacting galaxies

We present a systematic investigation of the star formation rate (hereafter SFR) in interacting disk galaxies. We determine the dependence of the overall SFR on different spatial alignments and impact parameters of more than 50 different configurations in combined N -body/hydrodynamic simulations. We also show mass profiles of the baryonic components. We find that galaxy–galaxy interactions can enrich the surrounding intergalatic medium with metals very efficiently up to distances of several 100 kpc. This enrichment can be explained in terms of indirect processes like thermal-driven galactic winds or direct processes like “kinetic” spreading of baryonic matter. In the case of equal mass mergers the direct–kinetic- redistribution of gaseous matter (after 5 Gyr) is less efficient than the environmental enrichment of the same isolated galaxies by a galactic wind. In the case of non-equal mass mergers however, the direct–kinetic- process dominates the redistribution of gaseous matter. Compared to the isolated systems, the integrated star formation rates (ISFRs) ($\int_{t\,=\,0~{\rm Gyr}}^{t\,=\,5~{\rm Gyr}}\textnormal{SFR(t)}{\rm d}t$) in the modelled interacting galaxies are in extreme cases a factor of 5 higher and on average a factor of 2 higher in interacting galaxies. Co-rotating and counter-rotating interactions do not show a common trend for the enhancement of the ISFRs depending on the interaction being edge-on or face-on. The latter case shows an increase of the ISFRs for the counter-rotating system of about 100%, whereas the edge-on counter-rotating case results in a lower increase (~10%). An increase in the minimum separation yields only a very small decrease in the ISFR after the first encounter. If the minimum separation is larger than ~$5\times$ the disk scale length R d the second encounter does not provide an enhancement for the ISFR.