Detailed observations and simulations of interacting galaxies in the nearby universe indicate that strong gravitational encounters between galaxies are capable of producing morphological distortions such as tidal tails, bridges and shells. In addition, these interactions can trigger episodes of intense star formation. These case studies suggest that the effects of interactions may persist long after these close encounters have taken place.
Using a large sample of galaxies from the Sloan Digital Sky Survey, we measure the influence of neighbouring galaxies on the morphologies and star formation rates of galaxies out to relatively wide pair separations. We find clear evidence of enhanced star formation out to pair separations of 150 kpc, and demonstrate that these enhancements are consistent with predictions from merger simulations. We also find evidence of enhanced asymmetry out to separations of 120 kpc. Together, these results show that the effects of interactions can be detected long after close encounters have occurred.
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