The distribution of mid- and far-infrared emission in 10 interacting galaxy systems

A sample of 10 interacting and merging galaxy systems has been mapped at mid-infrared (10 mu m) and far-infrared (100-160 mu m) wavelengths with spatial resolutions of 4" and 45", respectively, The interacting and merging systems are known to be strong IRAS sources; however, the IRAS dates contain limited information concerning the distribution of infrared emission between the two galaxies in each pair and no information on the distribution within each galaxy. The observations presented here show that in five of the seven paired systems, one galaxy is the dominant or the only infrared source. There is a good correlation between the H alpha and infrared emission levels for these galaxies, indicating that the infrared emission is closely tied to dust heated by young stars. There is also a good spatial correlation between the H alpha, infrared, and radio continuum morphologies of these systems, which further strengthens the belief that the infrared, as well as the radio emission, is associated with regions of active star formation. The 10 mu m emission is concentrated around the nuclei of most of these galaxies, indicating that the highest levels of current star formation activity are also confined to the near-nuclear regions. Some systems, however, show evidence for significant star formation activity throughout the outer disk regions of the galaxies. All the sample galaxies that are bright in the infrared also have optical indications of high levels of star formation or nuclear activity, suggesting that these conditions are necessary in order for a galaxy to exhibit excess infrared emission.