High-luminosity IRAS galaxies. I - The proportion of IRAS galaxies in interacting systems

An analysis of CCD images of a sample of 60 high-luminosity IRAS galaxies from the redshift survey of Lawrence et al. (1986) and of a control sample of 87 optically selected galaxies from the Durham redshift survey (Peterson et al., 1986) is presented. It is found that 18 + or - 5 percent of the optically selected galaxies are interacting or merging systems, and that 11 + or - 8 percent of the low-luminosity IRAS galaxies are interacting or merging. At high luminosities, the proportion is shown to be 46 + or - 12 percent. The results suggest that although galaxy interaction is a common causal factor in luminous IR activity, it is far from being the ubiquitous factor suggested in recent reports.