Molecular gas in strongly interacting galaxies. I. CO (1-0) observations

We present observations of the CO (1-0) line in 80 interacting galaxies as part of a program to study the role of interactions and mergers in triggeri ng starbursts. The sample, which only includes obviously interacting pairs of galaxies, is the largest such sample observed in CO. The observations we re carried out at the NRAO 12 m and IRAM 30 m telescopes. CO emission was d etected in 56 galaxies (of which 32 are new detections), corresponding to a detection rate of 70%. Because most galaxies are slightly larger than the telescope beam, correction factors were applied to include CO emission outs ide the beam. The correction factors were derived by fitting a Gaussian fun ction or an exponential CO brightness distribution to galaxies with multipl e pointings and by assuming an exponential model for galaxies with single p ointing. We compared the global CO fluxes of 10 galaxies observed by us at both telescopes. We also compared the measured fluxes for another 10 galaxi es observed by us with those by other authors using the NRAO 12 m and FCRAO 14 m telescopes. These comparisons provide an estimate of the accuracy of our derived global fluxes, which is similar to 40%. Mapping observations of two close pairs of galaxies, UGC 594 (NGC 317) and UGC 11175 (NGC 6621), a re also presented. In subsequent papers we will report the statistical anal yses of the molecular properties in our sample galaxies and make comparison s between isolated spirals and interacting galaxies.