Interacting galaxies in the IllustrisTNG simulations - I : Triggered star formation in a cosmological context

We use the IllustrisTNG cosmological hydrodynamical simulations to investigate how the specific star formation rates (sSFRs) of massive galaxies (M-* > 10(10) M-circle dot) depend on the distance to their closest companions. We estimate sSFR enhancements by comparing with control samples that are matched in redshift, stellar mass, local density, and isolation, and we restrict our analysis to pairs with stellar mass ratios of 0.1 to 10. At small separations (similar to 15 kpc), the mean sSFR is enhanced by a factor of 2.0 +/- 0.1 in the flagship (110.7Mpc)(3) simulation (TNG100-1). Statistically significant enhancements extend out to 3D separations of 280 kpc in the (302.6Mpc)(3) simulation (TNG300-1). We find similar trends in the EAGLE and Illustris simulations, although their sSFR enhancements are lower than those in TNG100-1 by about a factor of two. Enhancements in IllustrisTNG galaxies are seen throughout the redshift range explored (0Peer reviewe