THE MOLECULAR GAS—STAR FORMATION CONNECTION IN AN OPTICALLY-SELECTED SAMPLE OF INTERACTING GALAXIES

We have obtained 12 CO (1–0) emission-line observations for a sample of 37 interacting galaxy systems, chosen from a parent sample of optically-selected interacting galaxies. The sample observed here spans a large range of interaction strengths and current star formation rates. Using the standard Galactic CO-to-H2 conversion factor we find that the interacting galaxies are, on average, marginally more rich in molecular gas than a comparison sample of isolated spiral galaxies, having mean MH2/LB and MH2/MHI ratios that are 20–40% higher than that of the isolated spirals. The interacting galaxies have a mean LIR/MH2 ratio that is a factor of ∼1.3 higher than the isolated spirals, indicating that the rate of highmass star formation per unit molecular gas—the star formation efficiency—is also enhanced within the interacting galaxy sample. There is a strong correlation between relative H2 content and star formation